Sybase DC38133-01-0902-01 manual Ensuring consistent Message Agent settings, Management on

Chapter 10. SQL Remote Administration

enable recovery of data from system or media failure. In a replication installation, even if such recovery is achieved, the recovered database can be out of synch with remote databases. This can require a complete resynchronization of remote databases, which can be a formidable task if the installation involves large numbers of databases.

In short, recovery of the consolidated database from a failure at the consolidated site is only part of the task of recovering the entire replication installation.

	Protection of the replication system against media failures has two aspects:
	♦ Backup and log management	Solid backup procedures and log
	management procedures for the consolidated database server are an
	essential part of recovery plans. Backup procedures protect against media
	failure on the database device. Using a transaction log mirror protects
	against media failure on the transaction log device.
	☞ For more information about backup and log management procedures,
	see the sections “Transaction log and backup management” on page 249
	and “Adaptive Server Enterprise transaction log and backup
	management” on page 272 .
	♦ Message Agent configuration	The Message Agent command-line
	options provide ways for you to tune Message Agent behavior to match
	your backup and recovery requirements.
	Message Agent configuration is discussed in the following pages.
Replicating only	By default, the Message Agent processes all committed transactions. When
backed-up transactions	the Message Agent is run with the -uoption, only transactions that have
	been backed up by the database backup commands are processed.

For Adaptive Server Anywhere, transaction log backup is carried out using Sybase Central or the dbbackup utility, or off-line copying and renaming of the log file. For Adaptive Server Enterprise, transaction log backup is carried out using the dump transaction statement.

By sending only backed-up transactions, the replication installation is protected against media failure on the transaction log. Maintaining a mirrored transaction log also accomplishes this goal.

The -uoption provides additional protection against total site failure, if backups are carried out to another site.

Ensuring consistent Message Agent settings

Some Message Agent settings need to be the same throughout an installation, and so should be set before deployment. This section lists the

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