Contents IndexChapter 25.  Backup and Data Recovery The SQL Anywhere logs

User's Guide
   Part III. Using SQL Anywhere
     Chapter 25. Backup and Data Recovery
      System and media failures

SQL Anywhere has features to protect your data from two categories of computer failure: system failure and media failure.

System Failure A system failure occurs when a power failure or some other failure causes the computer or operating system to go down while there are partially completed transactions. This could occur when the computer is inappropriately turned off or rebooted, or when another application causes the operating system to crash.

Media Failure A media failure occurs when the database file, the file system, or the device storing the database file becomes unusable.

Recovery from failure

When failures occur, the SQL Anywhere recovery mechanism treats transactions properly, as atomic units of work: any incomplete transaction is rolled back and any committed transaction is preserved. This ensures that even in the event of failure, the data in your database remains in a consistent state.

SQL Anywhere uses three logs to protect your data from system. These log files exist for each database running on a database engine or server.

Make regular backups

You should make regular backups of your database files so that you can recover your database in the case of a media failure. SQL Anywhere uses the transaction log (which you should store on a separate device from the database for greater security) to recover information put into the database since the last full backup.

The SQL Anywhere Desktop Runtime database engine does not support a transaction log, so the work carried out between the time of the last backup and the time of the media failure is lost, and you will have to re-enter it into the database.

Contents IndexChapter 25.  Backup and Data Recovery The SQL Anywhere logs