How does the mirroring of log volumes work?
We recommend to mirror the log volumes using a RAID1 system. If this is not possible, the log volume should be mirrored by the database (parameter LOG_MIRRORED=YES). The database instance then uses two log volumes in parallel: • log entries are written to both volumes at the same time • log entries are read (during backup or restart) only from the primary log volume The entries on both log volumes can only be overwritten when a log backup has been performed. If an error is detected on one of the log volumes, this volume is marked as BAD and the database state is changed to OFFLINE. The corrupted log volume can then be recreated in ADMIN mode. During this recreation the complete content of the intact log volume is copied to the corrupted log volume. Afterwards the database can be restarted without a data loss. back to top Additional Information
