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SQL Anywhere 11.0.0 » SQL Anywhere Server - Database Administration » Maintaining Your Database » Backup and data recovery » Introduction to backup and recovery


Protecting your data against failure

If your database has become unusable, you have experienced a database failure. SQL Anywhere provides protection against the following categories of failure:

Media failure   The database file and/or the transaction log become unusable. This may occur because the file system or the device storing the database file becomes unusable, or it may be because of file corruption.

For example:

  • The disk drive holding the database file or the transaction log file becomes unusable.
  • The database file or the transaction log file becomes corrupted. This can happen because of hardware problems or software problems.

Backups protect your data against media failure.

See Understanding backups.

System failure   A system failure occurs when the computer or operating system goes down while there are partially completed transactions. This could occur when the computer is inappropriately turned off or restarted, when another application causes the operating system to crash, or because of a power failure.

For example:

  • The computer or operating system becomes temporarily unavailable while there are partially completed transactions, perhaps because of a power failure or operating system crash, or because the computer is inappropriately restarted.

After a system failure occurs, the database server recovers automatically when you next start the database. The results of each transaction committed before the system error are intact. All changes by transactions that were not committed before the system failure are canceled.

See Backup and recovery internals.

It is possible to recover uncommitted changes manually. See Recovering uncommitted operations.