Chapter 2: SQL Remote Replication Concepts

Data Replication with SQL Remote

Part 1 Introduction to SQL Remote

Chapter 1: Welcome to SQL Remote

Chapter 1

Welcome to SQL Remote

About this chapter

This chapter introduces SQL Remote and the documentation.

About SQL Remote

SQL Remote is a data-replication technology designed for two-way replication between a consolidated data server and large numbers of remote databases, typically including many mobile databases.

SQL Remote replication is message based, and requires no direct server-to-server connection. An occasional dial-up or e-mail link is sufficient.

Administration and resource requirements at the remote sites are minimal. The time lag between the consolidated and remote databases is configurable, and can range from minutes to hours or days.

Sybase SQL Remote technology is provided in two forms:

SQL Remote for Adaptive Server Anywhere
Enables replication between a consolidated Adaptive Server Anywhere database and a large number of remote databases.
SQL Remote for Adaptive Server Enterprise
Enables replication between a consolidated Adaptive Server Enterprise database and a large number of remote Adaptive Server Anywhere databases.

This book describes both of these technologies.

In a SQL Remote installation, you must have properly licensed SQL Remote software at each participating database.

For a detailed introduction to SQL Remote concepts and features, see SQL Remote Replication Concepts .

For a list of supported operating systems and message links, see Supported Platforms and Message Links .

About this manual

This manual describes how to design, build, and maintain SQL Remote installations.

The manual includes the following parts.

Introduction to SQL Remote
Replication concepts and features of SQL Remote.
Replication Design for SQL Remote
Designing SQL Remote installations.
SQL Remote Administration
Deploying SQL Remote databases and administering a running SQL Remote setup.
Reference
SQL Remote commands, system tables, and other reference material.

Platforms and products covered by this manual

This documentation applies to all supported platforms of SQL Remote. Not all features are available on all platforms. The operating systems and features you are entitled to use depends on the product you have purchased and your license agreement.

Available formats

The contents of this manual are provided online and in print. In some cases, the print documentation must be purchased separately.

Online documentation most current

The online documentation contains the most current information about SQL Remote. It is more authoritative than the printed manual.

Product installation

This section describes installation of SQL Remote for Adaptive Server Enterprise. If you obtained SQL Remote as part of another product, consult the installation instructions for the product you purchased.

To install the SQL Remote software for PC's:

Insert the CD-ROM into your CD-ROM drive.

If the installation program does not start automatically, start the setup application on the CD-ROM.

Follow the instructions in the installation program.

To install the SQL Remote software for UNIX:

Consult the instructions for your operating system in the Adaptive Server Anywhere Read Me First booklet.

If you are using SQL Remote for Adaptive Server Enterprise, you must install SQL Remote into any database you wish to replicate. For information about installing SQL Remote into a database, see Setting Up SQL Remote .

New features in version 6.0.3

In addition to bug fixes, SQL Remote version 6.0.3 includes the following new features. Features in Adaptive Server Anywhere that are particularly relevant to SQL Remote are also included in this list:

FTP and SMTP/POP support on UNIX
The range of message systems supported on UNIX operating systems has been expanded to include FTP and SMTP/POP.
For a listing of supported operating and message systems, see Supported Platforms and Message Links .
Message link options stored in the database
The message link parameters that control SQL Remote behavior over each message system can now be stored in the database as opposed to the registry. This simplifies deployment and management issues related to message link parameters.
For more information, see Setting message type control parameters , SET REMOTE OPTION statement , and sp_link_option procedure .
Date and time replication formats
You can now specify database options that instruct SQL Remote what format to use when replicating dates and times. These options are SR_time_format, SR_date_format, and SR_timestamp_format.
For more information, see Replication of dates and times , and SQL Remote options .
Message Agent and SQL Remote Open Server run as a daemon
On UNIX operating systems you can run these applications as a daemon using the -ud command-line option.
For more information, see The Message Agent , and The SQL Remote Open Server .
Easier unload and reload of Adaptive Server Anywhere databases
The dbunload utility has been enhanced (
```
-ar
```
command-line option) to allow a single-step unload and reload of a database that can be used whether or not your database is involved in replication.
For more information, see Unload utility options , and Unloading and reloading a database .
Enhanced dblog output
The dblog utility now displays additional summary information, including offset information.
For more information, see The DBLOG command-line utility .
dbtran utility enhancements
The dbtran command-line utility permits filtering of the transaction log operations to isolate subsets of operations. This is of particular use to SQL Remote administrators.
For more information, see The DBTRAN command-line utility .

Behavior changes

The following behavior has changed in version 6.0.3:

Message link parameters stored in the database
By default, the message link parameters are now moved into the database when the Message Agent is run for the first time with the new version of the software. If you have software that explicitly accesses these parameters in their old locations external to the database, it will be affected by this change. You can continue using the old behavior by setting the External_remote_options database option to ON.
Passwords stored
When a password is entered for a message link, it was not stored in previous versions of the software. As the parameters are now held in the database, a saved password is not held on disk and so is more secure. Passwords are now saved by default. You can continue using the old behavior by setting the Save_remote_passwords option to OFF.

Upgrade issues

You can use the version 6.0.3 software with your existing databases.

You must upgrade Adaptive Server Anywhere databases to version 6.0.3 of the software if you wish to take advantage of storing of message link parameters in the database, or if you wish to use the datetime replication options. You must upgrade the SQL Remote tables in your Adaptive Server Enterprise database to be able to use these features.

For information on upgrading Adaptive Server Anywhere databases, see ALTER DATABASE statement , or The Upgrade utility .

For information on upgrading Adaptive Server Enterprise databases, see Upgrading SQL Remote for Adaptive Server Enterprise .

New features in version 6.0.2

In addition to bug fixes, SQL Remote version 6.0.2 includes the following new features:

Performance enhancements
A major enhancement of the Adaptive Server Anywhere Message Agent (dbremote) operational model for scanning the transaction log and sending messages greatly improves the range of achievable replication turnaround times.
Minimum lag times between entering data at one site and its replication to another site were limited in earlier versions to times on the order of ten minutes. With the new operational model, minimum lag times on the order of seconds can be achieved in some circumstances.
When the Message Agent message-sending process runs in continuous mode, it now stays (hovers) at the end of the active transaction log while waiting for more data to be committed, instead of rescanning the transaction log each time. This allows you to poll more frequently, which can significantly reduce time for replication.
For more information, see Tuning Message Agent performance .
SQL Remote message logging
New command-line options allow you to tune message logging from these utilities.
For more information, see The Message Agent .


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