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Function documentation Log Settings Locate the document in the library structure

Use

You configure the most important properties for the logging of transactions in the log settings.

Note

In addition to the log settings, there are several database parameters that influence the logging of transactions.

Log Settings

Name

Description

Redo Log Management

Defines whether the database system writes redo log entries

·        Redo log management on: system default

·        Redo log management 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 the log backup history. If you have to restore the database instance after an error, no log entries are available for this period of time.

If redo log management was switched off and then you switch it back on, you then have to perform a complete data backup.

Overwrite Mode for the Log Area

Defines whether the database system is allowed to overwrite the log area even if the log entries have not been backed up.

·        Overwrite mode off: system default.

The database system can only overwrite the log area once the corresponding log entries have been backed up. To obtain a complete log backup history, you need to activate automatic log backup or regularly perform interactive backups.

·        Overwrite mode on:

The database system cyclically overwrites the log area without prior backups of the log entries. This interrupts the log backup history. This means that you cannot restore your database instance up to the last COMMIT before the system crashed, or up to any other time you choose, but only up to the time of the last data backup.

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

Log Mode

Defines whether the database system supports software-based mirroring.

·        No mirroring: system default

·        Mirroring: Use this setting only 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 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.

If there are problems accessing a log volume in the primary log area, the affected log volume is flagged as BAD, and the database instance is transferred to the OFFLINE operational state. To restore the defective log volume, replace the respective hard disk and, in the ADMIN operational state, copy the entire contents of the corresponding mirrored log volume to the primary log volume.

Activities

Database Manager GUI, Changing Log Settings

Database Manager CLI,

·        param_addvolume

·        medium_put

See also:

Backing Up Log Entries

 

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