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SQL Anywhere 12.0.0 » SQL Anywhere Server - Database Administration » Maintaining your database » Backup and data recovery » Types of backup » Live backups


Differences between live backups and transaction log mirrors

Both a live backup and a transaction log mirror provide a secondary copy of the transaction log. However, there are several differences between using a live backup and using a transaction log mirror:

  • In general, a live backup is made to a different computer   By running the Backup utility on a separate computer, the database server does not do the writing of the backed up log file, and the data transfer is done by the SQL Anywhere client/server communications system. Therefore, the performance impact is decreased and reliability is greater.

    Running a transaction log mirror on a separate computer is not recommended. It can lead to performance and data corruption problems, and stops the database server if the connection between the computers fails.

  • A live backup provides protection against a computer becoming unusable   Even if a transaction log mirror is kept on a separate device, it does not provide immediate recovery if the whole computer becomes unusable. You could consider an arrangement where two computers share access to a set of disks.

  • A live backup may lag behind the database server   A transaction log mirror contains all the information required for complete recovery of committed transactions. Depending on the load that the database server is processing, the live backup may lag behind the transaction log mirror and may not contain all the committed transactions.