Reliable Transaction Router
Getting Started
Order Number: AA-RLE1A-TE
January 2001
This document introduces Reliable Transaction Router and describes its
concepts for the system manager, system administrator, and applications
programmer.
Revision/Update Information:
Software Version:
This is a new manual.
Reliable Transaction Router Version 4.0
Compaq Computer Corporation
Houston, Texas
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Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
vii
1 Introduction
Reliable Transaction Router . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–1
1–2
1–3
1–15
1–23
RTR Continuous Computing Concepts . . . . . . . . . . . . . . . . . . . . .
RTR Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
RTR Server Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
RTR Networking Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 Architectural Concepts
The Three-Layer Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
RTR Facilities Bridge the Gap . . . . . . . . . . . . . . . . . . . . . . . . . . .
Broadcasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Flexibility and Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Transaction Integrity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Partitioned Data Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Object-Oriented Programming . . . . . . . . . . . . . . . . . . . . . . . . . . .
Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Class Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Polymorphism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Object Implementation Benefits . . . . . . . . . . . . . . . . . . . . . . .
XA Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2–1
2–3
2–3
2–3
2–4
2–5
2–5
2–7
2–8
2–8
2–9
2–9
2–10
iii
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3 Reliability Features
Servers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3–1
3–2
3–2
3–2
3–3
3–3
3–3
Failover and Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Router Failover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recovery Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Backend Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Router Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Frontend Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 RTR Interfaces
RTR Management Station . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
RTR Command Line Interface . . . . . . . . . . . . . . . . . . . . . . . .
Browser Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Application Programming Interfaces . . . . . . . . . . . . . . . . . . . . . .
RTR Object-Oriented Programming Interface . . . . . . . . . . . .
RTR C Programming Interface . . . . . . . . . . . . . . . . . . . . . . .
4–2
4–2
4–7
4–7
4–7
4–9
5 The RTR Environment
The RTR System Management Environment . . . . . . . . . . . . . . . .
Monitoring RTR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Transaction Management . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Partition Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The RTR Runtime Environment . . . . . . . . . . . . . . . . . . . . . . . . .
What’s Next? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5–1
5–4
5–4
5–5
5–5
5–7
Glossary
Index
Examples
2–1
Objects-Defined Sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2–8
iv
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Figures
1
RTR Reading Path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Client Symbol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Server Symbol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Roles Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Facility Symbol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Components in the RTR Environment . . . . . . . . . . . . . . . . . .
Two-Tier Client/Server Environment . . . . . . . . . . . . . . . . . . .
Three-Tier Client/Server Environment . . . . . . . . . . . . . . . . . .
Browser Applet Configuration . . . . . . . . . . . . . . . . . . . . . . . .
RTR with Browser, Single Node, and Database . . . . . . . . . . .
RTR Deployed on Two Nodes . . . . . . . . . . . . . . . . . . . . . . . . .
RTR Deployed on Three Nodes . . . . . . . . . . . . . . . . . . . . . . .
Standby Server Configuration . . . . . . . . . . . . . . . . . . . . . . . .
Transactional Shadowing Configuration . . . . . . . . . . . . . . . . .
x
1–4
1–1
1–2
1–3
1–4
1–5
1–6
1–7
1–8
1–9
1–10
1–11
1–12
1–13
1–14
1–5
1–6
1–6
1–7
1–9
1–9
1–10
1–11
1–11
1–12
1–13
1–14
Two Sites: Transactional and Disk Shadowing with Standby
Servers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–15
1–17
1–18
1–19
1–20
1–21
1–23
2–2
1–15
1–16
1–17
1–18
1–19
1–20
2–1
Standby Servers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Shadow Servers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Concurrent Servers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A Callout Server . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bank Partitioning Example . . . . . . . . . . . . . . . . . . . . . . . . . .
Standby with Partitioning . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Three Layer Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Partitioned Data Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
RTR Browser Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
RTR System Management Environment . . . . . . . . . . . . . . . .
RTR Runtime Environment . . . . . . . . . . . . . . . . . . . . . . . . . .
2–2
2–6
4–1
4–8
5–1
5–3
5–2
5–6
Tables
2–1
Functional and Object-Oriented Programming Compared . . .
2–7
v
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Preface
Purpose of this Document
The goal of this document is to assist an experienced system
manager, system administrator, or application programmer to
understand the Reliable Transaction Router (RTR) product.
Document Structure
This document contains the following chapters:
•
•
Chapter 1, Introduction to RTR, provides information on
RTR technology, basic RTR concepts, and RTR terminology.
Chapter 2, Architectural Concepts, introduces the RTR
three-layer model and explains ths use of RTR functions and
programming capabilities.
•
•
•
Chapter 3, Reliability Features, highlights RTR server types
and failover and recovery scenarios.
Chapter 4, RTR Interfaces, introduces the management and
programming interfaces of RTR.
Chapter 5, The RTR Environment, describes the RTR
system management and runtime environments, and
provides explicit pointers to further reading in the RTR
documentation set.
vii
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Related Documentation
Additional resources in the RTR documentation kit include:
Document
Content
F or a ll u ser s:
Reliable Transaction
Router Release Notes
Describes new features, changes, and
known restrictions for RTR.
RTR Commands
Lists all RTR commands, their
qualifiers and defaults.
F or th e system
m a n a ger :
Reliable Transaction
Router Installation
Guide
Describes how to install RTR on all
supported platforms.
Reliable Transaction
Router System
Describes how to configure, manage,
and monitor RTR.
Manager ’s Manual
Reliable Transaction
Router Migration
Guide
Explains how to migrate from RTR
Version 2 to RTR Version 3 (OpenVMS
only).
F or th e a p p lica tion
p r ogr a m m er :
Reliable Transaction
Router Application
Design Guide
Describes how to design application
programs for use with RTR, illustrated
with both the C and C++ interfaces.
Reliable Transaction
Router C++
Foundation Classes
Describes the object-oriented C++
interface that can be used to implement
RTR object-oriented applications.
Reliable Transaction
Router C Application
Programmer ’s
Explains how to design and code RTR
applications using the C programming
language; contains full descriptions of
the basic RTR API calls.
Reference Manual
You can find additional information on RTR and
existing implementations on the RTR web site at
viii
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Reader’s Comments
Compaq welcomes your comments on this guide. Please send
your comments and suggestions by email to rtrdoc@compaq.com.
Please include the document title, date from title page, order
number, section and page numbers in your message. For product
information, send email to rtr@compaq.com.
Conventions
This manual adopts the following conventions:
Convention
Description
New ter m
New terms are shown in bold when
introduced and defined. All RTR terms
are defined in the glossary at the end of
this document or in the supplemental
glossary in the RTR Application Design
Guide.
User input
User input and programming examples
are shown in a monospaced font.
Boldface monospaced font indicates
user input.
Terms and titles
Terms defined only in the glossary are
shown in italics when presented for
the first time. Italics are also used for
titles of manuals and books, and for
emphasis.
F E
TR
BE
RTR frontend
RTR transaction router or router
RTR backend
Reading Path
The reading path to follow when using the Reliable Transaction
Router information set is shown in Figure 1.
ix
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Cover
letter
SPD
Release
Notes
F
Getting
Started
Application Programmer
System Manager
Application
Design
Guide
Installation
Guide
If C++
If V2 to V3
C Application
Programmer's
Reference
Manual
C++
Foundation
Classes
System
Manager's
Manual
Migration
Guide
Commands
= Tutorial
ZKO-GS015-99AI
x
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1
Introduction
This document introduces RTR and describes RTR concepts. It is
intended for the system manager or administrator and for the
application programmer who is developing an application that
works with Reliable Transaction Router (RTR).
Reliable Transaction Router
Reliable Transaction Router (RTR) is failure-tolerant
transactional messaging middleware used to implement large,
distributed applications with client/server technologies. RTR
helps ensure business continuity across multivendor systems and
helps maximize uptime.
You use the architecture of RTR to ensure high availability and
transaction completion. RTR supports applications that run
on different hardware and different operating systems. RTR
also works with several database products including Oracle,
Microsoft Access, Microsoft SQL Server, Sybase, and Informix.
For specifics on operating systems, operating system versions,
and supported hardware, see the Reliable Transaction Router
Software Product Description for each supported operating
system.
Interoperability
RTR can be deployed in a local or wide area network and can use
either TCP/IP or DECnet for its underlying network transport.
Networking
Introduction 1–1
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RTR Continuous Computing Concepts
RTR Continuous Computing Concepts
RTR provides a continuous computing environment that is
particularly valuable in financial transactions, for example
in banking, stock trading, or passenger reservations systems.
RTR satisfies many requirements of a continuous computing
environment:
•
•
•
•
•
•
Reliability
Failure tolerance
Data and transaction integrity
Scalability
Ease of building and maintaining applications
Interoperability with multiple operating systems
RTR additionally provides the following capabilities, essential in
the demanding transaction processing environment:
•
•
•
•
•
•
Flexibility
Parallel execution at the transaction level
Potential for step-by-step growth
Comprehensive monitoring tools
Management station for single console system management
WAN deployability
RTR also ensures that transactions have the ACID properties.
A transaction with the ACID properties has the following
attributes:
•
•
•
•
Atomic
Consistent
Isolated
Durable
For more details on transactional ACID properties, see the
discussion later in this document, and in the RTR Application
Design Guide.
1–2 Introduction
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RTR Terminology
RTR Terminology
The following terms are either unique to RTR or redefined when
used in the RTR context. If you have learned any of these terms
in other contexts, take the time to assimilate their meaning in
the RTR environment. The terms are described in the following
order:
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Application
Client, client application
Server, server application
Channel
RTR configuration
Roles
Frontend
Router
Backend
Facility
Transaction
Transactional messaging
Nontransactional messaging
Transaction ID
Transaction controller
Standby server
Transactional shadowing
RTR journal
Partition
Key range
Introduction 1–3
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RTR Terminology
RTR Application
An RTR application is user-written software that executes
within the confines of several distributed processes. The RTR
application may perform user interface, business, and server
logic tasks and is written in response to some business need. An
RTR application can be written in any language, commonly C or
C++, and includes calls to RTR. RTR applications are composed
of two kinds of actors, client applications and server applications.
An application process is shown in diagrams as an oval, open for
a client application, filled for a server application.
A clien t is always a clien t a p p lica tion , one that initiates
and demarcates a piece of work. In the context of RTR, a client
must run on a node defined to have the frontend role. Clients
typically deal with presentation services, handling forms input,
screens, and so on. A client could connect to a browser running a
browser applet or be a webserver acting as a gateway. In other
contexts, a client can be a physical system, but in RTR and in
this document, physical clients are called frontends or nodes.
You can have more than one instance of a client on a node.
Client
Figure 1–1 Client Symbol
A ser ver is always a server application, one that reacts to a
client’s units of work and carries them through to completion.
This may involve updating persistent storage such as a database
file, toggling a switch on a device, or performing another
predefined task. In the context of RTR, a server must run on
a node defined to have the backend role. In other contexts,
a server can be a physical system, but in RTR and in this
document, physical servers are called backends or nodes. You
can have more than one instance of a server on a node. Servers
can have partition states such as primary, standby, or shadow.
Server
1–4 Introduction
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RTR Terminology
Figure 1–2 Server Symbol
RTR expects client and server applications to identify themselves
before they request RTR services. During the identification
process, RTR provides a tag or handle that is used for subsequent
interactions. This tag or handle is called an RTR ch a n n el. A
channel is used by client and server applications to exchange
units of work with the help of RTR. An application process can
have one or more client or server channels.
Channel
An RTR configuration consists of nodes that run RTR client
and server applications. An RTR configuration can run on
several operating systems including OpenVMS, Tru64 UNIX,
and Windows NT among others (for the full set of supported
operating systems, see the title page of this document, and the
appropriate SPD). Nodes are connected by network links.
RTR configuration
A node that runs client applications is called a fr on ten d
(FE), or is said to have the frontend role. A node that runs
server applications is called a ba ck en d (BE). Additionally, the
transaction r ou ter (TR) contains no application software but
acts as a traffic cop between frontends and backends, routing
transactions to the appropriate destinations. The router also
eliminates any need for frontends and backends to know about
each other in advance. This relieves the application programmer
from the need to be concerned about network configuration
details.
Roles
Introduction 1–5
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RTR Terminology
Figure 1–3 Roles Symbols
FE
BE
TR
The mapping between nodes and roles is done using a fa cility.
An RTR facility is the user-defined name for a particular
configuration whose definition provides the role-to-node map for
a given application. Nodes can share several facilities. The role
of a node is defined within the scope of a particular facility. The
router is the only role that knows about all three roles. A router
can run on the same physical node as the frontend or backend,
if that is required by configuration constraints, but such a setup
would not take full advantage of failover characteristics.
Facility
Figure 1–4 Facility Symbol
A facility name is mapped to specific physical nodes and their
roles using the CREATE FACILITY command.
Figure 1–5 shows the logical relationship between client
application, server application, frontends (FEs), routers (TRs),
and backends (BEs) in the RTR environment. The database is
represented by the cylinder. Two facilities are shown (indicated
by the large double-headed arrows), the user accounts facility
and the general ledger facility. The user accounts facility uses
three nodes, FE, TR, and BE, while the general ledger facility
uses only two, TR and BE.
Clients send messages to servers to ask that a piece of work be
done. Such requests may be bundled together into transactions.
An RTR transaction consists of one or more messages that have
been grouped together by a client application, so that the work
done as a result of each message can be undone completely, if
some part of that work cannot be done. If the system fails or is
1–6 Introduction
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RTR Terminology
Figure 1–5 Components in the RTR Environment
User Accounts Facility
FE
TR
BE
Client
application
Server
application
General Ledger Facility
LKG-11203-98WI
disconnected before all parts of the transaction are done, then
the transaction remains incomplete.
A tr a n sa ction is a piece of work or group of operations that
must be executed together to perform a consistent transformation
of data. This group of operations can be distributed across many
nodes serving multiple databases. Applications use services that
RTR provides.
Transaction
RTR provides transactional messaging in which transactions are
enclosed in messages controlled by RTR.
Transactional
messaging
Tr a n sa ction a l m essa gin g ensures that each transaction is
complete, and not partially recorded. For example, a transaction
or business exchange in a bank account might be to move money
from a checking account to a savings account. The complete
transaction is to remove the money from the checking account
and add it to the savings account.
A transaction that transfers funds from one account to another
consists of two individual updates: one to debit the first account,
and one to credit the second account. The transaction is not
complete until both actions are done. If a system performing
this work goes down after the money has been debited from the
checking account but before it has been credited to the savings
account, the transaction is incomplete. With transactional
Introduction 1–7
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RTR Terminology
messaging, RTR ensures that a transaction is ‘‘all or nothing’’—
either fully completed or discarded; either both the checking
account debit and the savings account credit are done, or the
checking account debit is backed out and not recorded in the
database. RTR transactions have the ACID properties.
An application will also contain nontransactional tasks such
as writing diagnostic trace messages or sending a broadcast
message about a change in a stock price after a transaction has
been completed.
Nontransactional
messaging
Every transaction is identified on initiation with a transaction
identifier or transaction ID, with which it can be logged and
tracked.
Transaction ID
To reinforce the use of these terms in the RTR context, this
section briefly reviews other uses of configuration terminology.
A traditional two-tier client/server environment is based on
hardware that separates application presentation and business
logic (the clients) from database server activities. The client
hardware runs presentation and business logic software, and
server hardware runs database or data manager (DM) software,
also called resource managers (RM). This type of configuration
is illustrated in Figure 1–6. (In all diagrams, all lines are
bidirectional.)
With the C++ API, the Transaction Controller manages
transactions (one at a time), channels, messages, and events.
Transaction
Controller
Further separation into three tiers is achieved by separating
presentation software from business logic on two systems,
and retaining a third physical system for interaction with the
database. This is illustrated in Figure 1–7.
RTR extends the three-tier model based on hardware to a
multitier, multilayer, or multicomponent software model.
1–8 Introduction
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RTR Terminology
Figure 1–6 Two-Tier Client/Server Environment
DM
Database Server
Application Presentation
and Business Logic
(ODBC Model)
LKG-11204-98WI
Figure 1–7 Three-Tier Client/Server Environment
DB
Server
Database
Application
Presentation/
User Interface
Application Server/
Business Logic
Database Server
LKG-11205-98WI
RTR provides a multicomponent software model where clients
running on frontends, routers, and servers running on backends
cooperate to provide reliable service and transactional integrity.
Application users interact with the client (presentation layer)
on the frontend node that forwards messages to the current
router. The router in turn routes the messages to the current,
appropriate backend, where server applications reside, for
processing. The connection to the current router is maintained
until the current router fails or connections to it are lost.
Introduction 1–9
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RTR Terminology
All components can reside on a single node but are typically
deployed on different nodes to achieve modularity, scalability,
and redundancy for availability. With different systems, if one
physical node goes down or off line, another router and backend
node takes over. In a slightly different configuration, you could
have an application that uses an external applet running on a
browser that connects to a client running on the RTR frontend.
Such a configuration is shown in Figure 1–8.
Figure 1–8 Browser Applet Configuration
PC Browser
Applet
RTR Frontend
Web Server
Process
RTR Client
Application
LKG-11206-98WI
The RTR client application could be an ASP (Active Server
Page) script or a process interfacing to the webserver through a
standard interface such as CGI (Common Gateway Interface).
RTR provides automatic software failure tolerance and failure
recovery in multinode environments by sustaining transaction
integrity in spite of hardware, communications, application,
or site failures. Automatic failover and recovery of service can
exploit redundant or underutilized hardware and network links.
As you modularize your application and distribute its
components on frontends and backends, you can add new
nodes, identify usage bottlenecks, and provide redundancy to
increase availability. Adding backend nodes can help divide
the transactional load and distribute it more evenly. For
example, you could have a single node configuration as shown in
Figure 1–9, RTR with Browser, Single Node, and Database. A
1–10 Introduction
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RTR Terminology
single node configuration can be useful during development, but
would not normally be used when your application is deployed.
Figure 1–9 RTR with Browser, Single Node, and Database
Browser
FE
TR
BE
DB
LKG-11207-98WI
When creating the configuration used by an application and
defining the nodes where a facility has its frontends, routers,
and backends, the setup must also define which nodes will
have journal files. Each backend in an RTR configuration must
have a journal file to capture transactions when other nodes
are unavailable. When applications are deployed, often the
backend is separated from the frontend and router, as shown in
Figure 1–10.
Figure 1–10 RTR Deployed on Two Nodes
Browser
DB
FE
TR
BE
Server
Client
Journal
LKG-11208-98WI
Introduction 1–11
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RTR Terminology
In this example, the frontend with the client and the router
reside on one node, and the server resides on the backend.
Frequently, routers are placed on backends rather than on
frontends. A further separation of workload onto three nodes is
shown in Figure 1–11.
Figure 1–11 RTR Deployed on Three Nodes
Browser
FE
TR
BE
DB
LKG-11209-98WI
This three-node configuration separates transaction load onto
three nodes, but does not provide for continuing work if one
of the nodes fails or becomes disconnected from the others. In
many applications, there is a need to ensure that there is a
server always available to access the database.
In this case, a sta n d by ser ver will do the job. A standby
server (see Figure 1–12 is a process that can take over when
the primary server is not available. Both the primary and
the standby server access the same database, but the primary
processes all transactions unless it is unavailable. The standby
processes transactions only when the primary is unavailable. At
other times, the standby can do other work. The standby server
is often placed on a node other than the node where the primary
server runs.
1–12 Introduction
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RTR Terminology
Figure 1–12 Standby Server Configuration
BE
Primary
Server
Server
TR
DB
BE
Standby
Server
Server
LKG-11210-98WI
To increase transaction availability, transactions can be
shadowed with a sh a d ow ser ver . This is called tr a n sa ction a l
sh a d ow in g and is accomplished by having a second location,
often at a different site, where transactions are also recorded.
This is illustrated in Figure 1–13. Data are recorded in two
separate data stores or databases. The router knows about both
backends and sends all transactions to both backends. RTR
provides the server application with the necessary information to
keep the two databases synchronized.
Transactional
shadowing
In the RTR environment, one data store (database or data
file) is elected the primary, and a second data store is made
the shadow. The shadow data store is a copy of the data store
kept on the primary. If either data store becomes unavailable,
all transactions continue to be processed and stored on the
surviving data store. At the same time, RTR makes a record
of (remembers) all transactions stored only on the shadow data
store in the RTR jou r n a l by the shadow server. When the
primary server and data store become available again, RTR
replays the transactions in the journal to the primary data store
through the primary server. This brings the data store back into
synchronization.
RTR Journal
Introduction 1–13
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RTR Terminology
Figure 1–13 Transactional Shadowing Configuration
BE
Primary
Server
Server
TR
FE
BE
Server
Shadow
Server
LKG-11211-98WI
With transactional shadowing, there is no requirement that
hardware, the data store, or the operating system at different
sites be the same. You could, for example, have one site
running OpenVMS and another running Windows NT; the RTR
transactional commit process would be the same at each site.
Note
Transactional shadowing shadows only transactions
controlled by RTR.
For full redundancy to assure maximum availability, a
configuration could employ both disk shadowing in clusters
at separate sites coupled with transactional shadowing across
sites with standby servers at each site. This configuration is
shown in Figure 1–14. For clarity, not all possible connections
are shown. In the figure, backends running standby servers are
shaded, connected to routers by dashed lines. Only one site (the
upper site) does full disk shadowing; the lower site is the shadow
for transactions, shadowing all transactions being done at the
upper site.
1–14 Introduction
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RTR Server Types
Figure 1–14 Two Sites: Transactional and Disk Shadowing with Standby Servers
BE
BE
Disk
Shadowing
TR
FE
BE
BE
TR
Transactional
Shadowing
LKG-11212-98WI
Standby Server or Router
RTR Server Types
In the RTR environment, in addition to the placement of
frontends, routers, and servers, the application designer must
determine what server capabilities to use. RTR provides four
types of software servers for application use:
•
•
Standby servers
Transactional shadow servers
Introduction 1–15
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RTR Server Types
•
•
Concurrent servers
Callout servers
These are described in the next few paragraphs. You specify
server types to your application in RTR API calls.
RTR server types help to provide continuous availability and a
secure transactional environment.
The sta n d by ser ver remains idle while the RTR primary
backend server performs its work, accepting transactions and
updating the database. When the primary server fails, the
standby server takes over, recovers any in-progress transactions,
updates the database, and communicates with clients until
the primary server returns. There can be many instances of a
standby server. Activation of the standby server is transparent
to the user.
Standby server
A typical standby configuration is shown in Figure 1–12,
Standby Server Configuration. Both physical servers running
the RTR backend software are assumed by RTR to connect
to the same database. The primary server is typically in use,
and the standby server can be either idle or used for other
applications, or data partitions, or facilities. When the primary
server becomes unavailable, the standby server takes over and
completes transactions as shown by the dashed line. Primary
server failure could be caused by server process failure or
backend (node) failure.
The intended and most common use of a standby server is in a
cluster environment. In a non- cluster environment, seamless
failover of standbys is not guaranteed.
Standby in a
cluster
Standby servers are ‘‘spare’’ servers which automatically
take over from the main backend if it fails. This takeover is
transparent to the application.
Figure 1–15 shows a simple standby configuration. The two
backend nodes are members of a cluster environment, and are
both able to access the database.
For any one key range, the main or primary server (Server)
runs on one node while the standby server (Standby) runs on
the other node. The standby server process is running, but RTR
does not pass any transactions to it. Should the primary node
fail, RTR starts passing transactions to (Standby). Note that
1–16 Introduction
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RTR Server Types
one node can contain the primary servers for one key range and
standby servers for another key range to balance the load across
systems. This allows the nodes in a cluster environment to act
as standby for other nodes without having idle hardware. When
setting up a standby server, both servers must have access to the
same journal.
Figure 1–15 Standby Servers
Terminals
Backends (BE)
Frontends (FE)
Routers (TR)
Database (DB)
FE
BE
Client
Server
FE
BE
DB
Client
Standby
TR
FE
Client
ZKO-GS013-99AI
The tr a n sa ction a l sh a d ow ser ver places all transactions
recorded on the primary server on a second database. The
transactional shadow server can be at the same site or at a
different site, and must exist in a networked environment.
Transactional
shadow server
A transactional shadow server can also have standby servers for
greater reliability. When one member of a shadow set fails, RTR
remembers the transactions executed at the surviving site in a
journal, and replays them when the failed site returns. Only
after all journaled transactions are recovered does the recovering
site receive new online transactions. Transactional shadowing
is done by partition. A transactional shadow configuration can
have only two members of the shadow set.
Shadow servers are servers on separate backends which handle
the same transactions in parallel on identical copies of the
database.
Introduction 1–17
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RTR Server Types
Figure 1–16 shows a simple shadow configuration. The main
(BE) Server at Site 1 and the shadow server (Shadow) at Site
2 both receive every transaction for the data partition they are
servicing. Should Site 1 fail, Site 2 continues to operate without
interruption. Sites can be geographically remote, for example,
available at separate locations in a wide area network (WAN).
Figure 1–16 Shadow Servers
Terminals
Backends (BE)
Frontends (FE)
Routers (TR)
Database (DB)
BE - SITE 1
Server
FE
Client
DB
BE - SITE 2
Shadow
FE
Client
DB
TR
FE
Client
ZKO-GS014-99AI
Note that each shadow server can also have standby servers.
The con cu r r en t ser ver is an additional instance of a server
application running on the same node. RTR delivers transactions
to a free server from the pool of concurrent servers. If one
server fails, the transaction in process is replayed to another
server in the concurrent pool. Concurrent servers are designed
primarily to increase throughput and can exploit Symmetric
Multiprocessing (SMP) systems. Figure 1–17, Concurrent
Servers, illustrates the use of concurrent servers sending
transactions to the same partition on a backend, the partition
A-N.
Concurrent server
Concurrent servers allow transactions to be processed in parallel
to increase throughput. Concurrent servers deal with the
same database partition, and may be implemented as multiple
1–18 Introduction
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RTR Server Types
channels within a single process or as one channel in separate
processes.
Figure 1–17 Concurrent Servers
BE
Server1
Server2
Server3
A-N
Server4
LKG-11275-98WI
The ca llou t ser ver provides message authentication on
transaction requests made in a given facility, and could be used,
for example, to provide audit trail logging. A callout server can
run on either backend or router nodes. A callout server receives
a copy of all messages in a facility. Because the callout server
votes on the outcome of each transaction it receives, it can veto
any transaction that does not pass its security checks.
Callout server
A callout server is facility based, not partition based; any
message arriving at the facility is routed to both the server
and the callout. A callout server is enabled when the facility is
defined. Figure 1–18 illustrates the use of a callout server that
authenticates every transaction (txn) in a facility.
To authenticate any part of a transaction, the callout server must
vote on the transaction, but does not write to the database. RTR
does not replay a transaction that is only authenticated.
Introduction 1–19
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RTR Server Types
Figure 1–18 A Callout Server
Callout
Server
User Accounts Facility
Application
Server
TR
BE
To
Transaction
Partition A
LKG-11276-98WI
RTR callout servers provide partition-independent processing for
authentication. For example, a callout server can enable checks
to be carried out on all requests in a given facility.
Authentication
Callout servers run on backend or router nodes. They receive a
copy of every transaction either delivered to or passing through
the node.
Callout servers offer the following advantages:
•
The security check can run in parallel with the database
updates thus improving response times.
•
•
The security check can be run on the router hardware.
The security checking code is completely separated from
other application code.
Since this technique relies on backing out unauthorized
transactions, it is most suitable when only a small proportion of
transactions are expected to fail the security check, so as not to
have a performance impact.
1–20 Introduction
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RTR Server Types
When working with database systems, partitioning the database
can be essential to ensuring smooth and untrammeled
performance with a minimum of bottlenecks. When you
p a r tition your database, you locate different parts of your
database on different disk drives to spread both the physical
storage of your database onto different physical media and to
balance access traffic across different disk controllers and drives.
Partition
For example, in a banking environment, you could partition
your database by account number, as shown in Figure 1–19. A
partition is a segment of your database.
Figure 1–19 Bank Partitioning Example
TR
Appn
Server - BE
Appn
Server - BE
Appn
Server - BE
Appn
Server - BE
Appn
Server - BE
Accts
40,000-
69,999
Accts
70,000-
89,999
Accts
Accts
20,000-
39,999
Accts
1-19,999
90,000-
99,999
LKG-11213-98WI
Once you have decided to partition your database, you use key
ranges in your application to specify how to route transactions
to the appropriate database partition. A k ey r a n ge is the
range of data held in each partition. For example, the key
range for the first partition in the bank partitioning example
goes from 00001 to 19999. You can assign a partition name in
your application program or have it set by the system manager.
Note that sometimes the terms key range and partition are
used as synonyms in code examples and samples with RTR,
Key range
Introduction 1–21
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RTR Server Types
but strictly speaking, the key range defines the partition. A
partition has both a name, its partition name, and an identifier
generated by RTR — the partition ID. The properties of a
partition (callout, standby, shadow, concurrent, key segment
range) can be defined by the system manager with a CREATE
PARTITION command. For details of the command syntax, see
the RTR System Manager ’s Manual.
A significant advantage of the partitioning shown in the bank
example is that you can add more account numbers without
making changes to your application; you need only add another
server and disk drive for the new account numbers. For example,
say you need to add account numbers from 90,000 to 99,999 to
the basic configuration of Figure 1–19, Bank Partitioning
Example. You can add these accounts and bring them on line
easily. The system manager can change the key range with a
command, for example, in an overnight operation, or you can
plan to do this during scheduled maintenance.
A partition can also have multiple standby servers.
A node can be configured as a primary server for one key range
and as a standby server for another key range. This helps
to distribute the work of the standby servers. Figure 1–20
illustrates this use of standbys with distributed partitioning.
As shown in Figure 1–20, Application Server A is the primary
server for accounts 1 to 19,999 and Application Server B is the
standby for these same accounts. Application Server B is the
primary for accounts 20,000 to 39,999 and Application Server A
can be the standby for these same accounts (not shown in the
figure). For clarity, account numbers are shown only for primary
servers and one standby server.
Standby Server
Configurations
RTR supports anonymous clients, that is, clients can be set up in
a configuration using wildcarded node names.
Anonymous clients
Tunnel
RTR can also be used with firewall tunneling software, which
supports secure internet communication for an RTR connection,
either client-to-router, or router-to-backend.
1–22 Introduction
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RTR Networking Capabilities
Figure 1–20 Standby with Partitioning
Application
1-19999
1-19999
ServerA
Accounts:
1-19999
Router
1-19999
1-19999
Application
20000-39999
ServerB
20000-39999
20000-39999
LKG-11214-98WI
RTR Networking Capabilities
Depending on operating system, RTR uses TCP/IP or DECnet
as underlying transports for the virtual network (RTR facilities)
and can be deployed in both local area and wide area networks.
PATHWORKS 32 is required for DECnet configurations on
Windows NT.
Introduction 1–23
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2
Architectural Concepts
This chapter introduces concepts on basic transaction processing
and RTR architecture.
The Three-Layer Model
RTR is based on a three-layer architecture consisting of frontend
(FE) roles, backend (BE) roles and router (TR) roles. The roles
are shown in Figure 2–1. In this and subsequent diagrams,
rectangles represent physical nodes, ovals represent application
software, and DB represents the disks storing the database (and
usually the database software that runs on the server).
Client processes run on nodes defined to have the frontend role.
This layer allows computing power to be provided locally at the
end-user site for transaction acquisition and presentation.
Server processes (represented by ‘‘Server’’ in Figure 2–1) run on
nodes defined to have the backend role. This layer:
•
•
Allows the database to be distributed geographically.
Permits replication of servers to cope with either network,
node or site failures.
•
Allows computer resources to be added to meet performance
requirements.
Architectural Concepts 2–1
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The Three-Layer Model
Figure 2–1 The Three Layer Model
Terminals
Backends (BE)
Frontends (FE)
Routers (TR)
Database (DB)
BE
FE
Client
Server
DB
DB
DB
BE
FE
Client
Server
TR
TR
BE
FE
Client
Server
FE
Client
ZKO-GS011-99AI
•
Allows performance or geographic expansion while protecting
the investments made in existing hardware and application
software.
The router layer contains no application software unless running
callout servers. This layer reduces the number of logical network
links required on frontend and backend nodes. It also decouples
the backend layer from the frontend layer so that configuration
changes in the (frequently changing) user environment have
little influence on the transaction processing and database
(backend) environment.
The three layer model can be mapped to any system topology.
More than one role may be assigned to any particular node.
For example, on a system with few frontends, the router and
frontend layers can be combined in the same nodes. During
application development and test, all three roles can be combined
in one node.
The nodes used by an application and their configuration
roles are specified using RTR configuration commands. RTR
lets application code be completely location and configuration
independent.
2–2 Architectural Concepts
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RTR Facilities Bridge the Gap
RTR Facilities Bridge the Gap
Many applications can use RTR at the same time without
interfering with one another. This is achieved by defining a
separate facility for each application.
When an application calls the rtr_open_channel( ) routine to
declare a channel as a client or server, it specifies the name of
the facility it will use.
See the RTR System Manager ’s Manual for information on how
to define facilities.
Broadcasts
Sometimes an application has a requirement to send unsolicited
messages to multiple recipients.
An example of such an application is a commodity trading
system, where the clients submit orders and also need to be
informed of the latest price changes.
The RTR broadcast capability meets this requirement.
Recipients subscribe to a class of broadcasts; a sender broadcasts
a message in this class, all interested recipients receive the
message.
RTR permits clients to broadcast messages to one or more
servers, or servers to broadcast to one or more clients. If a server
needs to broadcast a message to another server, it must open a
second channel as a client.
Flexibility and Growth
RTR allows you to cope easily with changes in:
Network demand
•
Architectural Concepts 2–3
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Flexibility and Growth
•
•
User access patterns
The volume of data
Since an RTR-based system can be built using multiple systems
at each functional layer, it easily lends itself to step-by-step
growth, avoiding unused capacity at each stage. With your
system still up and running, it is possible to:
•
•
Create and delete concurrent server processes.
Add or remove nodes (frontend, router or backend).
This means you do not need to provide spare capacity to allow
for growth.
RTR also allows parallel execution. This means that different
parts of a single transaction can be processed in parallel by
multiple servers.
RTR provides a comprehensive set of monitoring tools to help you
evaluate the volume of traffic passing through the system. This
can help you respond to unexpected load changes by altering the
system configuration dynamically.
Transaction Integrity
RTR greatly simplifies the design and coding of distributed
applications, because, with RTR, database actions can be
bundled together into transactions.
To ensure that your application deals with transactions correctly,
its transactions must be:
•
•
•
•
Atomic
Consistent
Isolated
Durable
These are the ACID properties of transactions. For more
detail on these properties, see the Reliable Transaction Router
Application Design Guide.
2–4 Architectural Concepts
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The Partitioned Data Model
The Partitioned Data Model
One goal in designing for high transaction throughput is
reducing the time that users must wait for shared resources.
While many elements of a transaction processing system can be
duplicated, one resource that must be shared is the database.
Users compete for a shared database in three ways:
•
•
•
For use of the disk
For locks on database records
For the CPU resources needed to access the database
This competition can be alleviated by spreading the database
across several backend nodes, each node being responsible for a
subset of the data, or partition. RTR enables you to implement
this partitioned data model, shown roughly in Figure 2–2 where
the database has three partitions. RTR routes messages to the
correct partition on the basis of an application-defined key. For a
more complete description of partitioning as provided with RTR,
see the Reliable Transaction Router Application Design Guide.
Object-Oriented Programming
The C++ foundation classes map traditional RTR functional
programming concepts into an object-oriented programming
model. Using the power and features of these foundation
classes requires a basic understanding of the differences
between functional and object-oriented programming concepts.
Table 2–1 compares the worlds of functional programming and
object-oriented programming.
Architectural Concepts 2–5
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Object-Oriented Programming
Figure 2–2 Partitioned Data Model
Terminals
Backends (BE)
Frontends (FE)
Routers (TR)
Database (DB)
BE
FE
Client
Server
DB
DB
DB
BE
FE
Client
Server
TR
TR
BE
FE
Client
Server
FE
Client
ZKO-GS012-99AI
2–6 Architectural Concepts
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Object-Oriented Programming
Table 2–1 Functional and Object-Oriented Programming
Compared
Functional Programming
Object-Oriented Programming
A program consists of data
structures and algorithms.
A program consists of a team of
cooperating objects.
The basic programming
unit is the function, that
when run, implements an
algorithm.
The basic programming
unit is the class, that when
instantiated, implements an
object.
Functions operate on
elemental data types or
data structures.
Objects communicate by sending
messages.
An application’s architecture
consists of a hierarchy of
functions and sub-functions.
An applications architecture
consists of objects that model
entities of the problem domain.
Objects’ relationships can vary.
In the object-oriented environment, a program or application
is a grouping of cooperating objects. The basic programming
unit is the class. Instantiating, or declaring an instance of,
a class implements an object. RTR provides object-oriented
programming capabilities with the C++ API, described in the
C++ Foundation Classes manual. Objects are instances of a
class. In a transaction class, each transaction is an object. An
object is an instantiated (declared) class. Its state and behavior
are determined by the attributes and methods defined in the
class. An object or class is defined by its:
Objects
•
•
•
State (attributes)
Behavior (methods)
Identity (name at instantiation)
The name given at object declaration is its identity. In
Example 2–1, the two dog objects King and Fifi are instances
of Dog. The Dog class is declared in a header (Dog.h) file and
implemented in a .cpp file.
Architectural Concepts 2–7
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Object-Oriented Programming
Example 2–1 Objects-Defined Sample
Dog.h:
class Dog
{ ...
};
main.cpp:
#include "Dog.h"
main()
{
Dog King;
Dog Fifi;
}
Objects communicate by sending messages. This is done by
calling an object’s methods.
Messages
Some principal categories of messages are:
•
•
•
Constructors: Create objects
Destructors: Delete objects
Selectors: Return part or all of an object’s state. For
example, a Get method
•
•
Modifiers: Change part or all of an object’s state. For
example, a Set method
Iterators: Access multiple element objects within a container
object. For example, an array.
Classes can be related in the following ways:
Class
Relationships
•
•
•
Simple association: One class is aware of another class. For
example, "Dog object is associated with a Master object." This
is a "Knows a" relationship.
Composition: One class contains another class as part of its
attributes. For example, "Dog objects contains Leg objects."
This is a "Has a" relationship.
Inheritance A child class is derived from one or more parent,
or base, classes. For example, "Mutt object derives from
Collie object and Boxer object which both derive from Dog
object." This is an "Is a" relationship. Inheritance enables
the use of polymorphism.
2–8 Architectural Concepts
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Object-Oriented Programming
Polymorphism is the ability of objects, inherited from a common
base or parent class, to respond differently to the same message.
This is done by defining different implementations of the same
method name within the individual child class definitions. For
example: A DogArray object, "DogArray OurDogs[2];" refers to
two element objects of class Dog, the base class:
Polymorphism
•
•
King, of class Doberman, is a derived or child class of Dog.
Fifi, of class Minipoodle, is a derived or child class of Dog.
If, in a program, OurDogs[n]->Bark( ) is called in a loop, then:
•
•
In iteration one ([1]), method King::Bark( ) is called.
In iteration two ([2]), method Fifi::Bark( ) is called.
King’s bark does not sound like Fifi’s bark because each Bark( )
call is a separately defined method within its child object
definition. The virtual parent class (Dog) method Bark( ) is
defined in the class definition of Dog.
The benefits of creating RTR solutions with C++ foundation
classes include the following:
Object
Implementation
Benefits
•
•
•
•
•
•
Each major RTR concept is represented by its own individual
foundation class.
Simple methods within RTR classes transform features of
RTR for streamlined solutions.
Major classes include Get and Set methods for changing
transaction states.
Default handling code is provided for all Messages and
Events, where appropriate.
You do not need to provide handling code for all messages
and events.
The sending and receiving of data is abstracted to a higher
level with transaction controller and data classes.
•
•
No buffers and links coding is needed.
Internal RTR information is accessible without a need to
know RTR internals.
Architectural Concepts 2–9
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XA Support
XA Support
The XA interface is part of the X/Open DTP (Distributed
Transaction Processing) standard. It defines the interface that
transaction managers (TM) and resource managers (RM) use
to perform the two-phase commit protocol. (Resource managers
are underlying database systems such as ORACLE RDBMS,
Microsoft SQL Server, and others.) This interface is not used by
the application programs; it is only used by TM-to-RM exchanges
to coordinate a transaction.
For details on using XA, see the RTR C Application
Programmer ’s Reference Manual and the RTR Application
Design Guide.
2–10 Architectural Concepts
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3
Reliability Features
Reliability in RTR is enhanced by the use of:
•
•
•
•
•
Concurrent servers
Standby servers
Shadow servers
Callout servers
Router failover
Servers
Note that, conceptually, servers can be contrasted as follows:
•
•
•
•
Concurrent servers handle similar transactions which access
the same data partition and run on the same node.
Shadow servers handle the same transactions and run on
different nodes.
Standby servers provide a node that can take over processing
on a data partition when the primary server or node fails.
Callout servers run on backends or routers and receive all
messages within a facility so that authentication and logging
operations can be performed in parallel.
All servers are further described in the earlier section on RTR
Terminology.
Reliability Features 3–1
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Failover and Recovery
Failover and Recovery
RTR provides several capabilities to ensure failover and recovery
under several circumstances.
Frontend nodes automatically connect to another router if the
one being used fails. This reconnection is transparent to the
application.
Router Failover
Routers are responsible for coordinating the two-phase commit
for transactions. If the original router coordinating a transaction
fails, backend nodes select another router that can ensure correct
transaction completion.
Transactions in the process of being committed at the time of a
failure are recovered from RTR’s disk journal. Recovery could be
with a concurrent server, a standby server, or a restarted server
created when the failed backend restarts.
Backend
Restart
Recovery
Correct ordering of the execution of transactions against the
database is maintained.
Transaction messages which are lost in transit are re-sent when
possible. The frontend and backend nodes keep an in-memory
copy of all active messages for this purpose.
Transaction
Message
Replay
In the event of a communications failure, RTR tries to reconnect
the link or links until it succeeds.
Link Failure
Recovery
Recovery Scenarios
This section describes how RTR recovers from different hardware
and software failure. For additional information on failure and
recovery scenarios, see the RTR Application Design Guide.
3–2 Reliability Features
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Recovery Scenarios
If standby or shadow servers are available on another backend
node, operation of the rest of the system will continue without
interruption, using the standby or shadow server.
Backend
Recovery
If a backend processor is lost, any transactions in progress
are remembered by RTR and later recovered, either when the
backend restarts, or by a standby if one is present. Thus, the
distributed database is brought back to a transaction-consistent
state.
If a router fails and another router node is available, all in-
progress transactions are transparently re-routed by the other
router. System operation will continue without interruption.
Router
Recovery
If a frontend is lost:
Frontend
Recovery
•
All transactions committed but not completed on the frontend
node at the time of failure will be completed.
•
All transactions started but not committed on the frontend
node at the time of failure will be aborted.
Reliability Features 3–3
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4
RTR Interfaces
RTR provides interfaces for management and application
programming.
You manage RTR with a management interface from the RTR
management station. The management interfaces are:
•
•
The command line interface or CLI
The browser interface
The application programming interfaces (APIs) are:
•
The object-oriented API for C++ programming, available with
RTR Version 4.0. Use this API for all new development and,
where appropriate, for new work on existing applications.
An application can contain both object-oriented classes and
portable API calls. This API can be used to implement
applications on all platforms supported by RTR.
•
•
The RTR API for C programming, available with RTR V3.
This interface is also called the Portable API because it can
be used to implement applications on all platforms supported
by RTR.
The OpenVMS API containing OpenVMS calls, available
with RTR V2. This API, supported on OpenVMS only, is
obsolete for new development. While applications using this
API should be rewritten in the new object-oriented API to
take advantage of new RTR features and capabilities, they
can be changed by adding object-oriented classes rather than
being rewritten.
You can use the command line interface to the API to write
simple RTR applications for testing and experimentation. The
CLI is described in the Reliable Transaction Router System
Manager ’s Manual. Its use is illustrated in this chapter.
RTR Interfaces 4–1
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The RTR application programming interfaces are identical
on all hardware and operating system platforms that support
RTR. The object-oriented API is fully described in the manual
Reliable Transaction Router C++ Foundation Classes. The C-
programming API is fully described in the Reliable Transaction
Router C Application Programmer ’s Reference Manual. Both
APIs are used in designs in the RTR Application Design Guide.
RTR Management Station
You can manage RTR from a node on which RTR is running,
from a remote node from which you send RTR commands to a
node running RTR, or from a browser. The node where you enter
commands, interact with the browser, or view results is your
management station.
The command line interface (CLI) to the RTR API enables the
programmer to write short RTR applications from the RTR
command line. This can be useful for testing short program
segments and exploring how RTR works. For example, the
following sequence of commands starts RTR and exchanges a
message between a client and a server. To use these examples,
you execute RTR commands simulating your RTR client
application on the frontend and commands simulating your
server application on the backend.
RTR Command
Line Interface
Note
The channel identifier identifies the application process
to the ACP. The client and server process must each have
a unique channel identifier. In this example, the channel
identifier for the client is C and for the server is S. Both
use the facility called DESIGN.
The following example shows communication between a client
and a server created by entering commands at a terminal
keyboard. The client application is executing on the frontend
and the server on the backend.
4–2 RTR Interfaces
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RTR Management Station
The user is called user, the facility being defined is called
DESIGN, a client and a server are established, and a test
message containing the words "Kathy’s text today" is sent from
the client to the server. After the server receives this text, the
user on the server enters the words "And this is my response."
System responses begin with the characters % RTR-. Notes on
the procedure are enclosed in square brackets [ ]. For clarity,
commands you enter are shown in bold. You can view the status
of a transaction with the SHOW TRANSACTION command.
The exchange of messages you observe in executing these
commands illustrates RTR activity. You need to retain a similar
sequence in your own designs for starting up RTR and initiating
your own application.
You can use RTR SHOW and MONITOR commands to display
status and examine system state at any time from the CLI.
For more information on RTR commands, see the Reliable
Transaction Router System Manager ’s Manual.
Note
The rtr_receive_message command waits or blocks
if no message is currently available. When using the
rtr_receive_message command in the RTR CLI, use the
/TIME=0 qualifier or TIMEOUT to poll for a message, if
you do not want your rtr_receive_message command to
block.
RTR Interfaces 4–3
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RTR Management Station
[The user issues the following commands on the server
application where RTR is running on the backend.]
$ RTR
Copyright Compaq Computer Corporation 1994.
RTR> set mode/group
%RTR-I-STACOMSRV, starting command server on node NODEA
%RTR-I-GRPMODCHG, group changed from " " to "username"
%RTR-I-SRVDISCON, server disconnected on node NODEA
RTR> CREATE JOURNAL
%RTR-I-STACOMSRV, starting command server on node NODEA in group "username"
%RTR-S-JOURNALINI, journal has been created on device D:
RTR> SHOW JOURNAL
Journal configuration on NODEA in group "username" at Mon Aug 28 14:54:11 2000:-
Disk:
D:\ Blocks:
1000
RTR> start rtr
%RTR-I-NOLOGSET, logging not set
%RTR-S-RTRSTART, RTR started on node NODEA in group "username"
RTR> CREATE FACILITY DESIGN/ALL_ROLES=(NODEA)
[- or /all=NODEA,NODEB]
%RTR-S-FACCREATED, facility DESIGN created
RTR> SHOW FACILITY
Facilities on node NODEA in group "username" at Mon Aug 28 15:00:28 2000:
Facility
DESIGN
Frontend
yes
Router
yes
Backend
yes
RTR> rtr_open/server/accept_explicit/prepare_explicit/chan=s/fac=DESIGN
%RTR-S-OK, normal successful completion
RTR> RTR_RECEIVE_MESSAGE/CHAN=S
%RTR-S-OK, normal successful completion
channel name: S
.
.
.
msgtype:
rtr_mt_opened
.
.
.
status:
normal successful completion
[When the next command is issued, RTR waits for a message
from the client.]
4–4 RTR Interfaces
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RTR Management Station
RTR> RTR_RECEIVE_MESSAGE/CHAN=S
%RTR-S-OK, normal successful completion
channel name: S
msgsb
msgtype:
msglen:
usrhdl:
Tid:
rtr_mt_msg1
19
0
63b01d10,0,0,0,0,2e59,43ea2002
message
offset bytes
text
000000 4B 61 74 68 79 27 73 20 74 65 78 74 20 74 6F 64 Kathy’s text tod
000010 61 79 00
reason:
ay.
Ox00000000
RTR> RTR_REPLY_TO_CLIENT/CHAN=S "And this is my response."
%RTR-S-OK, normal successful completion
RTR> show transaction
Frontend transactions on node NodeA in group "username" at Mon Aug 28 15:12:10 2000
Tid
Facility
DESIGN
FE-User
State
SENDING
63b01d10,0,0,0,0,2e59,43ea2002
username.
Router transactions on node NodeA in group "username" at Mon Aug 28 15:12:10 2000:
63b01d10,0,0,0,0,2e59,43ea2002
DESIGN
username.
SENDING
Backend transactions on node NodeA in group "username" at Mon Aug 28 15:12:10 2000:
63b01d10,0,0,0,0,2e59,43ea2002
DESIGN
username.
RECEIVING
RTR> RTR_RECEIVE_MESSAGE/CHAN=S
%RTR-S-OK, normal successful completion
channel name: S
msgsb
msgtype:
rtr_mt_prepare
[if OK, use: RTR_ACCEPT_TX
else, use: RTR_REJECT_TX]
RTR> RTR_RECEIVE_MESSAGE/TIME=0
RTR> STOP RTR [Ends example test.]
[Commands and system response at client.]
$ RTR
RTR> START RTR
%RTR-S-RTRSTART, RTR started on node NODEA in group "username"
RTR> RTR_OPEN_CHANNEL/CHANNEL=C/CLIENT/fac=DESIGN
%RTR-S-OK, normal successful completion
RTR Interfaces 4–5
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RTR Management Station
RTR> RTR_RECEIVE_MESSAGE/CHANNEL=C/tim
[to get mt_opened or mt_closed]
%RTR-S-OK, normal successful completion
channel name: C
msgsb
msgtype:
msglen:
rtr_mt_opened
8
message
status:
reason:
normal successful completion
Ox00000000
RTR> RTR_START_TX/CHAN=C
%RTR-S-OK, normal successful completion
RTR> RTR_SEND_TO_SERVER/CHAN=C "Kathy’s text today." [text sent to the server]
%RTR-S-OK, normal successful completion
RTR> show transaction
Frontend transactions on node NodeA in group "username" at Mon Aug 28 15:05:43 2000
Tid
Facility
DESIGN
FE-User
State
SENDING
63b01d10,0,0,0,0,2e59,43ea2002
username.
Router transactions on node NodeA in group "username" at Mon Aug 28 15:06:43 2000:
63b01d10,0,0,0,0,2e59,43ea2002
Backend transactions on node NodeA in group "username" at Mon Aug 28 15:06:43 2000:
63b01d10,0,0,0,0,2e59,43ea2002 DESIGN username. SENDING
DESIGN
username.
SENDING
RTR> RTR_RECEIVE_MESSAGE/TIME=0/CHAN=C
[The following lines arrive at the client from RTR after the user
enters commands at the server.]
%RTR-S-OK, normal successful completion
channel name: C
msgsb
msgtype:
msglen:
usrhdl:
tid:
rtr_mt_reply
25
0
63b01d10,0,0,0,0,2e59,43ea2002
message
offset bytes
text
000000 41 6E 64 20 74 68 69 73 20 69 73 20 6D 79 20 72 And this is my r
000010 65 73 70 6F 6E 73 65 2E 00
esponse..
RTR> RTR_ACCEPT_TX/CHANNEL=C
%RTR-S-OK, normal successful completion
RTR> show transaction
Frontend transactions on node NodeA in group "username" at Mon Aug 28 15:17:45 2000
Tid
Facility
DESIGN
FE-User
State
VOTING
63b01d10,0,0,0,0,2e59,43ea2002
username.
Router transactions on node NodeA in group "username" at Mon Aug 28 15:17:45 2000:
63b01d10,0,0,0,0,2e59,43ea2002
DESIGN
username.
VOTING
Backend transactions on node NodeA in group "username" at Mon Aug 28 15:17:45 2000:
63b01d10,0,0,0,0,2e59,43ea2002
DESIGN
username.
COMMIT
4–6 RTR Interfaces
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RTR Management Station
RTR> RTR_RECEIVE_MESSAGE
%RTR-S-OK, normal successful completion
channel name: S
.
.
.
msgtype: rtr_mt_accepted
.
.
.
RTR> STOP RTR
With the RTR browser interface, your management station has
a network-browser-like display from which you can view RTR
status and issue RTR certain commands with a point-and-click
operation, rather than by entering commands. Figure 4–1 shows
one screen of the browser interface as you may view it from your
management station running Microsoft Internet Explorer. Not
all RTR CLI commands are accessible to the browser interface,
only the most commonly used commands are available with the
RTR browser. The browser interface provides help (for forms
input) and logging windows, and navigational aids between
displays.
Browser
Interface
Application Programming Interfaces
You write application programs and management applications
with the RTR application programming interfaces.
You can use the object-oriented programming interface to
write C++ applications that use RTR. For more information on
the object-oriented programming interface, see the RTR C++
Foundation Classes manual and the RTR Application Design
Guide.
RTR
Object-Oriented
Programming
Interface
RTR Interfaces 4–7
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Application Programming Interfaces
Figure 4–1 RTR Browser Interface
Example of object creation in an RTR client program.
Sample C++ client
code
//
// Create a Transaction Controller to receive incoming messages
// and events from a client.
//
RTRClientTransactionController *pTransaction = new RTRClientTransactionController();
//
// Create an RTRData object to hold an ASCII message for the server.
//
RTRData *pMessage1 = new RTRData("You are pretty easy to use!!!");
//
// Send the Server a message
//
sStatus = pTransaction->SendApplicationMessage(pMessage1);
ASSERT(RTR_STS_OK == sStatus);
//
// Since we have successfully finished our work, tell RTR we accept the
// transaction.
//
pTransaction->AcceptTransaction();
4–8 RTR Interfaces
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Application Programming Interfaces
Example of object creation in an RTR server program.
Sample C++
server code
void CombinationOrderProcessor::StartProcessingOrdersAtoL()
{
//
// Create an RTRKeySegment for all ASCII values between "A" and "L."
//
m_pkeyRange = new RTRKeySegment (rtr_keyseg_string, //To process strings.
1,
//Length of the key.
OffsetIntoApplicationProtocol, //Offset value.
"A",
//Lowest ASCII value for partition.
//Highest ASCII value for partition.
"L");
StartProcessingOrders(PARTITION_NAMEAToL,m_pKeyRange);
}
//
// Create an RTRData Oobject to hold each incoming message or event. This
// object will be reused.
//
RTRData *pDataReceived= new RTRData();
//
// Continually loop, receiving messages and dispatching them to the handlers.
//
while(true)
{
sStatus = pTransaction->Receive(&pDataReceived);
ASSERT(RTR_STS_OK == sStatus);
sStatus = pDataReceived->Dispatch();
ASSERT(RTR_STS_OK == sStatus);
}
You can use the C programming interface to write C applications
that use RTR. For more information on the C programming
interface, see the RTR C Application Programmer ’s Reference
Manual and the RTR Application Design Guide.
RTR C
Programming
Interface
Snippets from client and server programs using the RTR C-
programing API follow and are more fully shown in the RTR
Application Design Guide.
RTR Interfaces 4–9
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Application Programming Interfaces
Example of an open channel call in an RTR client program:
Sample C client
code
status = rtr_open_channel(&Channel,
Flags,
Facility,
Recipient,
RTR_NO_PEVTNUM,
Access,
RTR_NO_NUMSEG,
RTR_NO_PKEYSEG);
if (Status != RTR_STS_OK)
Example of a receive message call in an RTR server program:
Sample C server
code
status = rtr_receive_message(&Channel,
RTR_NO_FLAGS,
RTR_ANYCHAN,
MsgBuffer,
DataLen,
RTR_NO_TIMOUTMS,
&MsgStatusBlock);
if (status != RTR_STS_OK)
A client can have one or multiple channels, and a server can
have one or multiple channels. A server can use concurrent
servers, each with one channel. How you create your design
depends on whether you have a single CPU or a multiple CPU
machine, and on your overall design goals and implementation
requirements.
4–10 RTR Interfaces
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5
The RTR Environment
The RTR environment has two parts:
•
•
The system management environment
The runtime environment
The RTR System Management Environment
You manage your RTR environment from a management station,
which can be on a node running RTR or on some other node.
You can manage your RTR environment either from your
management station running a network browser, or from the
command line using the RTR CLI. From a managment station
using a network browser, processes use the http protocol for
communication.
The RTR system management environment contains four
processes:
•
•
•
•
The RTR Control Process, RTRACP
The RTR Command Line Interface, RTR CLI
The RTR Command Server Process, RTRCOMSERV
The RTR daemon, RTRD
The RTR Control Process, RTRACP, is the master program.
It resides on every node where RTR has been installed and is
running. RTRACP performs the following functions:
•
•
Manages network links
Sends messages between nodes
The RTR Environment 5–1
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The RTR System Management Environment
•
Handles all transactions and recovery
RTRACP handles interprocess communication traffic, network
traffic, and is the main repository of runtime information. ACP
processes operate across all RTR roles and execute certain
commands both locally and at remote nodes. These commands
include:
•
•
•
•
•
FACILITY
SET LINK/NODE
SET/CREATE PARTITION
SHOW NODE
STOP RTR
RTR CLI is the Command Line Interface that:
•
•
Accepts commands entered locally by the system manager
Sends commands to the Command Server Process
RTRCOMSERV
•
Can initiate commands on one node and execute them on
another in most cases
Commands executed directly by the CLI include:
•
•
•
•
•
•
•
DISPLAY
DO (to the local operating system)
MONITOR commands
RECALL
SET ENVIRONMENT
SPAWN
HELP
RTR COMSERV is the Command Server Process that:
•
•
•
Receives commands from RTR
Remains temporarily waiting for another command
Exits automatically when idle for some time
5–2 The RTR Environment
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The RTR System Management Environment
The Command Server Process executes commands both locally
and across nodes. Commands that can be executed at the RTR
COMSERV include:
•
•
•
START RTR
CREATE/MODIFY J OURNAL
SHOW LINK/FACILITY/SERVER/CLIENT (ACP must be
running)
•
Application programmer commands (for testing and
demonstration)
The RTR system management environment is illustrated in
Figure 5–1.
Figure 5–1 RTR System Management Environment
TR
BE
FE
RTRACP
RTRACP
RTRACP
RTRD
RTRD
RTRD
RTR
COMSERV
RTR
RTR
COMSERV
RTR CLI
COMSERV
RTR CLI
LKG-11216-98WI
Management
Station
Running
Browser
Software
The RTR Environment 5–3
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The RTR System Management Environment
RTR Monitor pictures or the RTR Monitor let you view the
Monitoring RTR
status and activities of RTR and your applications. A monitor
picture is dynamic, its data periodically updated. RTR SHOW
commands that also let you view status are snapshots, giving
you a view at one moment in time. A full list of RTR Monitor
pictures is available in the RTR System Manager ’s Manual ‘‘RTR
Monitoring’’ chapter and in the help file under RTR_Monitoring.
Many RTR Monitor pictures are available using the RTR browser
interface.
The RTR transaction is the heart of an RTR application,
and transaction state characterizes the current condition of a
transaction. As a transaction passes from one state to another, it
undergoes a state transition. Transaction states are maintained
in memory, and some are stored in the RTR journal for use in
recovery.
Transaction
Management
RTR uses three transaction states to track transaction status:
•
•
•
transaction runtime state
transaction journal state
transaction server state
Transaction runtime state describes how a transaction progresses
from the point of view of RTR roles (FE, TR, BE). A transaction,
for example, can be in one state as seen from the frontend, and
in another as seen from the router.
Transaction journal state describes how a transaction progresses
from the point of view of the RTR journal. The transaction
journal state, not seen by frontends and routers, managed by
the backend, is used by RTR for recovery replay of a transaction
after a failure.
Transaction server state, also managed by the backend, describes
how a transaction progresses from the point of view of the
server. RTR uses this state to determine if a server is available
to process a new transaction, or if a server has voted on a
particular transaction.
The RTR SHOW TRANSACTION command shows transaction
status, and the RTR SET TRANSACTION command can be
used, under certain well-constrained circumstances, to change
the state of a live transaction. For more details on use of SHOW
and SET commands, see the RTR System Manager ’s Manual.
5–4 The RTR Environment
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The RTR System Management Environment
Partitions are subdivisions of a routing key range of values used
with a partitioned data model and RTR data-content routing.
Partitions exist for each range of values in the routing key for
which a server is available to process transactions. Redundant
instances of partitions can be started in a distributed network,
to which RTR automatically manages the state and flow of
transactions. Partitions and their characterisitcs can be defined
by the system manager or operator, as well as within application
programs.
Partition
Management
RTR management functions enable the operation to manage
many partition-based attributes and functions including:
•
•
•
•
Creation/deletion of a partition with a user-specified name
Defining/changing a key-range definition
Selecting a preferred primary node
Selecting failover precedence between local and cross-site
shadows
•
•
•
Suspending/resuming operations to synchronize database
backup with transaction flow
Overriding the automatic recovery procedures of RTR with
manual recovery procedures, for added flexibility
Specifying retry limits for problem transactions
The operator can selectively inspect transactions, modify states,
or remove transactions from the journal or the running RTR
system. This allows for greater operational control and enhanced
management of a system where RTR is running.
For more details on managing partitions and their use in
applications, see the RTR System Manager ’s Manual chapter
‘‘Partition Management.’’
The RTR Runtime Environment
When all RTR and application components are running, the RTR
runtime environment contains:
•
Client application
The RTR Environment 5–5
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The RTR Runtime Environment
•
•
•
•
Server application
RTR shareable image, LIBRTR
RTR control process, RTRACP
RTR daemon, RTRD
Figure 5–2 shows these components and their placement on
frontend, router, and backend nodes. The frontend, router, and
backend can be on the same or different nodes. If these are all
on the same node, there is only one RTRACP process.
Figure 5–2 RTR Runtime Environment
TR
BE
LIBRTR/RTRDLL
FE
LIBRTR/RTRDLL
LIBRTR/RTRDLL
Server
Application
Client
Application
RTRACP
RTRD
RTRACP
RTRD
RTRACP
RTRD
RTR
COMSERV
RTR
COMSERV
RTR
COMSERV
RTR CLI
RTR CLI
Optional
External
Applet
Not Running
RTR
LKG-11215-98WI
5–6 The RTR Environment
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What’s Next?
What’s Next?
This concludes the material on RTR concepts and capabilities
that all users and implementors should know. For more
information, proceed as follows:
If you are:
Read these documents:
a system manager, system
administrator, or software
installer
1. RTR Release Notes
2. RTR Installation Guide
3. RTR Migration Guide (if
upgrading from RTR V2 to V3)
4. RTR System Manager ’s
Manual
an applications or system
management developer,
programmer, or software
engineer
RTR Application Design Guide
RTR C++ Foundation Classes
RTR C Application
Programmer ’s Reference Manual
The RTR Environment 5–7
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Glossary
A few additional terms are defined in the Glossary to the
Reliable Transaction Router Application Design Guide.
ACID
Transaction properties supported by RTR: atomicity, consistency,
isolation, durability.
ACP
The RTR Application Control Process.
API
Application Programming Interface.
applet
A small application designed for running on a browser.
application
User-written software that uses employs RTR.
application classes
The C++ API classes used for implementing client and server
applications.
backend
BE, the physical node in an RTR facility where the server
application runs.
bank
An establishment for the custody of money, which it pays out on
a customer ’s request.
Glossary–1
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branch
A subdivision of a bank; perhaps in another town.
broadcast
A nontransactional message.
callout server
A server process used for transactional authentication.
channel
A logical port opened by an application with an identifier to
exchange messages with RTR.
client
A client is always a client application, one that initiates and
demarcates a piece of work. In the context of RTR, a client must
run on a node defined to have the frontend role. Clients typically
deal with presentation services, handling forms input, screens,
and so on. A browser, perhaps running an applet, could connect
to a web application that acts as an RTR client, sending data to
a server through RTR.
In other contexts, a client can be a physical system, but in the
context of RTR and in this document, such a system is always
called a frontend or a node.
client classes
C++ foundation classes used for implementing client
applications.
commit process
The transactional process by which a transaction is prepared,
accepted, committed, and hardened in the database.
commit sequence number (CSN)
A sequence number assigned to an RTR commit group,
established by the vote window, the time interval during which
transaction response is returned from the backend to the router.
All transactions in the commit group have the same CSN and
lock the database.
Glossary–2
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common classes
C++ foundation classes that can be used in both client and server
applications.
concurrent server
A server process identical to other server processes running on
the same node.
CPU
Central processing unit.
data marshalling
The capability of using systems of different architectures (big
endian, little endian) within one application.
data object
See RTRData object.
deadlock
Deadly embrace, a situation that occurs when two transactions
or parts of transactions conflict with each other, which could
violate the consistency ACID property when committing them to
the database.
disk shadowing
A process by which identical data are written to multiple disks to
increase data availability in the event of a disk failure. Used in
a cluster environment to replicate entire disks or disk volumes.
See also transactional shadowing.
dispatch
A method in the C++ API RTRData class which, when called,
interprets the contents on the RTRData object and calls an
appropriate handler to process the data. The handler chosen to
process the data is the handler registered with the transaction
controller. This method is used with the event-driven receive
model.
DTC
Microsoft Distributed Transaction Coordinator.
Glossary–3
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endian
The byte-ordering of multibyte values. Big endian: high-order
byte at starting address; little endian: low-order byte at starting
address.
event
RTR or application-generated information about an application
or RTR.
event driven
A processing model in which the application receives messages
and events by registering handlers with the transaction
controller. These handlers are derived from the C++ foundation
class message and event-handler classes.
event handler
A C++ API-derived object used in event-driven processing that
processes events.
facility
The mapping between nodes and roles used by RTR and
established when the facility is created.
facility manager
A C++ API management class that creates and deletes facilities.
facility member
A defined entity within a facility. A facility member is a role and
node combined. Can be a client, router or server.
failover
The ability to continue operation on a second system when the
first has failed or become disconnected.
failure tolerant
Software that enables an application to continue when failures
such as node or site outages occur. Failover is automatic.
fault tolerant
Hardware built with redundant components to ensure that
processing survives component failure.
Glossary–4
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frontend
FE, the physical node in an RTR facility where the client
application runs.
FTP
File transfer protocol.
inquorate
Nodes/roles that cannot participate in a facility’s transactions
are inquorate.
journal
A file containing transactional messages used for recovery.
key range
An attribute of a key segment, for example a range A to E or F
to K.
key segment
An attribute of a partition that defines the type and range of
values that the partition handles.
LAN
Local area network.
link
A communications path between two nodes in a network.
local node
The node on which a C++ API client or server application runs.
The local node is the computer on which this instance of the RTR
application is executing.
management classes
C++ API classes used by new or existing applications to manage
RTR.
member
See facility member.
Glossary–5
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message
A logical grouping of information transmitted between software
components, typically over network links.
message handler
A C++ API-derived object used in event-driven processing that
processes messages.
multichannel
An application that uses more than one channel. A server is
usually multichannel.
multithreaded
An application that uses more than one thread of execution in a
single process.
MS DTC
Microsoft DTC; see DTC.
node
A physical system.
nontransactional message
A message containing data that does not contain any part of
a transaction such as a broadcast or diagnostic message. See
transactional message.
partition
RTR transactions can be sent to a specific database segment
or partition. This is data content routing and handled by RTR
when so programmed in the application and specified by the
system administrator. A partition can be in one of three states:
primary, standby, and shadow.
partition properties
Information about the attributes of a partition.
polling
A processing method where the application polls for incoming
messages.
Glossary–6
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primary
The state of the partition servicing the original data store or
database. A primary has a secondary or shadow counterpart.
process
The basic software entity, including address space, scheduled by
system software, that provides the context in which an image
executes.
properties
Application, transaction and system information.
property classes
Classes used for obtaining information about facilities, partitions,
and transactions.
quorate
Nodes/roles in a facility that has quorum are quorate.
quorum
The minimum number of routers and backends in a facility,
usually a majority, who must be active and connected for the
valid completion of processing.
quorum node
A node, defined specified in a facility as a router, whose purpose
is not to process transactions but to ensure that quorum
negotiations are possible.
quorum threshold
The minimum number of routers and backends in a facility
required to achieve quorum.
roles
Roles are defined for each node in an RTR configuration based on
the requirements of a specific facility. Roles are frontend, router,
or backend.
Glossary–7
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rollback
When a transaction has been committed on the primary
database but cannot be committed on its shadow, the committed
transaction must be removed or rolled back to restore the
database to its pre-transaction state.
router
The RTR role that manages traffic between RTR clients and
servers.
RTR configuration
The set of nodes, disk drives, and connections between them
used by RTR.
RTR environment
The RTR run-time and system management areas.
RTRData object
An instance of the C++ API RTRData class. This object contains
either a message or an event. It is used for both sending and
receiving data between client and server applications.
secondary
See shadow.
server
A server is always a server application or process, one that
reacts to a client application’s units of work and carries them
through to completion. This may involve updating persistent
storage such as a database file, toggling the switch on a device,
or performing another pre-defined task. In the context of RTR, a
server must run on a node defined to have the backend role.
In other contexts, a server may be a physical node, but in RTR
and in this document, physical servers are called backends or
nodes.
server classes
C++ foundation classes used for implementing server
applications.
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shadow
The state of the server process that services a copy of the data
store or primary database. In the context of RTR, the shadow
method is transactional shadowing, not disk shadowing. Its
counterpart is primary.
SMP
Symmetric MultiProcessing.
standby
The state of the partition that can take over if the process for
which it is on standby is unavailable. It is held in reserve, ready
for use.
TPS
Transactions per second.
transaction
An operation performed on a database, typically causing an
update to the database. Analogous in many cases to a business
transaction such as executing a stock trade or purchasing an
item in a store. A business transaction may consist of one or
more than one RTR transaction. A transaction is classified as
original, replay, or recovery, depending on how it arrives at the
backend:
Original—Transaction arrived on the first attempt from the
client.
Replay—Transaction arrived after some failure as the
result of a re-send from the client (that is, from the client
transaction-replay buffers in the RTRACP).
Recovery—Transaction arrived as the result of a backend-
to-backend recovery operation (recovery from the
journal).
transaction controller
A transaction controller processes transactions. A transaction
controller may have 0 or 1 transactions active at any moment in
time. It is through the transaction controller that messages and
events are sent and received.
Glossary–9
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transactional message
A message containing transactional data.
transactional shadowing
A process by which identical transactional data are written
to separate disks often at separate sites to increase data
availability in the event of site failure. See also disk shadowing.
two-phase commit
A database commit/rollback concept that works in two steps: 1.
The coordinator asks each local recovery manager if it is able
to commit the transaction. 2. If and only if all local recovery
managers agree that they can commit the transaction, the
coordinator commits the transaction. If one or more recovery
managers cannot commit the transaction, then all are told to roll
back the transaction. Two- phase commit is an all-or-nothing
process: either all of a transaction is committed, or none of it is.
WAN
Wide area network.
Glossary–10
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Index
DECnet, 1–23
Distributed applications, 2–4
DTP standard, 2–10
A
ACID, 2–4
Anonymous client, 1–22
API, 4–1
Application
distributed, 2–4
software, 2–2
Authentication, 1–20
F
Facility, 2–3
Failure tolerance, 3–2
Fault tolerance, 3–2
FE, 2–1
Firewall tunneling software, 1–22
Frontend, 2–1
B
CPU loss, 3–3
Backend, 2–1
loss, 3–3
BE, 2–1
Broadcast, 2–3
K
Key range, 1–16
C
L
Callout
LAN, 1–23
server, 1–20, 3–1
Client
anonymous, 1–22
processes, 2–1
Concurrent server, 3–1
Link failure recovery, 3–2
Load balance, 1–17
Lock
database, 2–5
M
D
Microsoft SQL Server, 2–10
Database, 2–1, 2–2
locks, 2–5
shared, 2–5
Data model
partitioned, 2–5
Index–1
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Server (cont’d)
shadow, 3–1
spare, 1–16
standby, 3–1
types, 3–1
N
Network
wide area, 1–18
Shadow
Nodes, 2–2
server, 1–17, 3–1
Shared database, 2–5
Spare server, 1–16
SQL
server, 2–10
Standby
O
Object-oriented, 2–5
Oracle
RDBMS, 2–10
server, 3–1
Subscribe, 2–3
P
Parallel execution, 2–4
Partitioned data model, 2–5
Processes
T
TCP/IP, 1–23
client, 2–1
server, 2–1
Three-layer model, 2–1
TM, 2–10
TR, 2–1
Transaction, 2–4
integrity, 2–4
replay, 3–2
Transaction manager, 2–10
Tunnel, 1–22
R
RDBMS, 2–10
Recovery, 3–2
Reliability features, 3–1
Resource manager, 2–10
RM, 2–10
Two-phase commit, 3–2
Router, 2–1
W
WAN, 1–23
failover, 3–2
layer, 2–2
loss, 3–3
Wide area network, 1–18
RTR
API, 4–1
X
broadcasts, 2–3
facilities, 2–3
flexibility and growth, 2–3
reliability features, 3–1
X/Open DTP, 2–10
XA
interface, 2–10
S
Security
check, 1–20
Server
callout, 3–1
concurrent, 3–1
Index–2
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