Procedure documentationConfiguring Logging Locate this document in the navigation structure


The database system logs all transactions that change application data or the database catalog in log entries. The database system uses these log entries to roll back or repeat SQL statements, if necessary.


Use one of the following database tools:

Database Studio, Database Manager CLI, or CCMS (in SAP systems only)

  1. To specify the most important logging properties, use the log settings.

    Log Settings



    Log mode

    Specifies whether the database system supports software-based mirroring.

    • Log area not mirrored: System default value

    • Log area mirrored (software-based): Only use this setting if hardware-based mirroring is not possible. Software-based mirroring reduces the performance of your database system.

      In software-based mirroring, the database system writes redo log entries to two log areas in parallel (primary and secondary log area). The database system can only overwrite the log areas when the log entries in the primary log area have been backed up.

    Overwrite mode for the log area

    Specifies whether the database system can overwrite redo log entries in the log area even if they have not been backed up.

    • Overwrite mode is off:

      The database system can only overwrite the log area once the corresponding redo log entries have been backed up. We therefore recommend that you activate the automatic log backup function or perform interactive backups regularly.

    • Overwrite mode on:

      The database system cyclically overwrites the log area without first backing up the redo log entries. This results in gaps in the backup history. This, in turn, means that you can only restore your database up to the time of the last data backup.

    If overwrite mode is on and you switch it off, you then have to execute a complete data backup.

    Redo log management

    Specifies whether the database system writes redo log entries.

    • Redo log management is on:

      System default value

    • Redo log management is off:

      In rare cases, it may make sense to switch off redo log management, for example during a big load job. Note that this interrupts the log backup history. If you have to restore the database after an error, no redo log entries are available for this period of time. Thus you lose the data since the last data backup.

    If redo log management is off and you switch it on, you then must perform a complete data backup.

    More information:

  2. To specify further logging properties, for example log segment size and number of log volumes, use database parameters.

    More information: Database Parameters

  3. If you need to increase the log area, add log volumes.

    More information:

More Information

Concepts of the Database System, How Databases Log Data Changes