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SQL Anywhere 11.0.1 (Français) » SQL Anywhere Server - Database Administration » Replication » Replicating data with Replication Server » Using the LTM


Transaction log and backup management

One of the differences between the Adaptive Server Enterprise LTM and the SQL Anywhere LTM is that while the Adaptive Server Enterprise LTM depends on a temporary recovery database for access to old transactions, the SQL Anywhere LTM depends on access to old transaction logs. No temporary recovery database exists for the SQL Anywhere LTM.

Replication depends on access to operations in the transaction log, and for SQL Anywhere primary site databases, sometimes access to old transaction logs. This section describes how to set up backup procedures at a SQL Anywhere primary site to ensure proper access to old transaction logs.

Consequences of lost transaction logs

Good backup practices at SQL Anywhere primary database sites are crucial. A lost transaction log could mean rematerializing replicate site databases. At primary database sites, a transaction log mirror is recommended.

For information about transaction log mirrors and other backup procedure information, see Transaction log mirrors, and Backup and data recovery.

The LTM configuration file contains a directory entry, which points to the directory where backed up transaction logs are kept. This section describes how to set up a backup procedure to ensure that such a directory stays in proper shape.

Backup utility options

With the Backup utility, you have the option of renaming the transaction log on backup and restart. For the dbbackup utility, this is the -r option. It is recommended that you use this option when backing up the primary database and replication database transaction logs.

For example, consider a database named primedb.db, in directory c:\prime, with a transaction log in directory d:\primelog\primedb.log. Backing up this transaction log to a directory e:\primebak using the rename and restart option performs the following tasks:

  1. Backs up the transaction log, creating a backup file e:\primebak\primedb.log.

  2. Renames the existing transaction log to d:\primelog\YYMMDDxx.log, where xx are sequential characters ranging from AA to ZZ.

  3. Starts a new transaction log, as d:\primelog\primedb.log.

    After several backups, the directory d:\primelog contains a set of sequential transaction logs. The log directory should not contain any transaction logs other than the sequence of logs generated by this backup procedure.

  4. Modify the LTM configuration file and set SQL_log_files to d:\primelog instead of e:\primebak. The e:\primebak directory is only used for recovery, not log scanning.

Using the delete_old_logs option
The Unload utility and replication