You use log settings to configure logging transactions.
Log settings
Name |
Description |
Redo log management |
Defines whether the database system writes redo log entries · Redo log management is switched on: System default · Redo log management switched off: In rare cases, it may make sense to switch off redo log management, for example when the database instance is initialized. Note that this interrupts the log backup history. In other words, no log entries are available for this period if a recovery is necessary. If redo log management was switched off and is then switched on again, you then have to perform a complete data backup. |
Overwrite mode for the log area |
Defines whether the database system may overwrite the log area without making a log backup beforehand. · Overwrite mode switched off: System default. The log area can only be overwritten once the corresponding log entries have been backed up. You therefore have to switch on automatic log backup or perform interactive log backups regularly. In this way you ensure a complete log backup history if you need to restore data. · Overwrite mode switched on: The log area is cyclically overwritten without backing up the log entries beforehand. As a result, the log backup history is interrupted. If a recovery is required, only those log entries that are in the log area are available. In general 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. Only switch on overwrite mode if it is sufficient for your system security that you can only restore the system to the status of the last data backup. If overwrite mode was switched on and you switch back to normal log backup operation, you then have to perform 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. During mirroring, the database system writes to both log areas in parallel. They cannot be overwritten until the log entries for the first log area are backed up. For a restart or for the log backup, only log entries from the primary log area are read. If there are problems with accessing a log area, the relevant log volume is marked as BAD and the database instance is transferred to the OFFLINE operational state. You can then restore the defective log volume in operational state ADMIN. This copies the complete content of the corresponding log volume from the other log area to the defective log volume. |
See also:
Database Manager GUI, Changing Log Settings
Database Manager CLI, Changing Volume Parameters