SQL Remote replication places new requirements on data recovery practices at consolidated database sites. Standard backup and recovery procedures 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:

Replicating only backed-up transactions

By default, the Message Agent processes all committed transactions. When the Message Agent is run with the -u option, only transactions that have been backed up by the database backup commands are processed.

Transaction log backup is carried out using Sybase Central or the dbbackup utility, or off-line copying and renaming of the log file.

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