When flashback mode is turned off all flashback logs are deleted ONLY if there’s no guaranteed restore points. Other than that flashback logs are deleted according to the below: Thus, retention of flashback logs and other files required to satisfy the guaranteed restore point, in addition to files required to satisfy the backup retention policy, can cause the fast recovery area to fill completely. No file in the fast recovery area is eligible for deletion if it is required to satisfy a guaranteed restore point. In this case, any flashback logs that would require the use of that redo log file for the use of FLASHBACK DATABASE are also deleted. If the fast recovery area is full, then an archived redo log that is reclaimable according to the FRA rules may be automatically deleted by the fast recovery area to make space for other files.
#Oracle 10g faq answers full#
If the database must create a new flashback log and the fast recovery area is full or there is no disk space, then the oldest flashback log is reused instead. If a flashback log is old enough that it is no longer needed to satisfy the flashback retention target, then a flashback log is reused.
If the fast recovery area has enough space, then a flashback log is created whenever necessary to satisfy the flashback retention target. However, if there’s space pressure in the Flash Recovery Area (FRA), flashback logs may be deleted to make room for other things, like backups and archived logs, for example. Oracle will try to keep as much Flashback logs as needed to satisfy the DB_FLASHBACK_RETENTION_TARGET parameter. They are not needed for media recovery.Ī: Flashback logs are managed by Oracle only. Even if the command BACKUP RECOVERY AREA is used to backup the contents of the FRA to tape only the following file types are backed up: full and incremental backup sets, control file autobackups, datafile copies, and archived redo logs.įlashback Logs are considered to be transient files and cannot be backed up by RMAN. Q: Can RMAN be used to backup flashback logs?Ī: No. UPDATE: For large 11.1.0.7+ databases with more than a 4GB SGA, you may consider setting LOG_BUFFER to values in the range of 32-64 MB. The size of the Flashback Buffer is set to 2 * LOG_BUFFER.įor performance reasons, it’s recommended to set LOG_BUFFER to at least 8MB for Q: Is it possible to specify the size of the Flashback Buffer in the SGA?Ī: Yes, but indirectly. If there isn’t a Guaranteed Restore Point and it’s a standby database, the database will hang until the cause of the write failure is fixed. If there isn’t a Guaranteed Restore Point and it’s a primary database, the Flashback Mode will be automatically turned off for the database, which will continued to operate normally. If there’s a Guaranteed Restore Point, the database crashes to ensure the restore point guarantee is not voided. Q: What happens if RVWR cannot write to disk?Ī: It depends on the context where the write error occurs: This guarantees that the database can be flashbacked to the exact point-in-time when the flashback mode was turned on. Once flashback is turned on Oracle starts to save the before-images of the database blocks before they are changed. In 10g Release 2 the database must be mounted, but not open. Q: Do I need to shutdown and mount the database to turn flashback on?Ī: ALTER DATABASE FLASHBACK ON is an online operation in 11g Release 2. RVWR (Recovery Writer, a.k.a Flashback Writer) was introduced in Oracle 10g to write flashback data from the Flashback Buffer in the SGA to the flashback database logs on disk. Q: Is there a separate background process for writing flashback logs?Ī: Yes. Some of the questions couldn’t be answered during the meeting so I’ve followed up on them and I’m posting the answers here since they may be of interest for many others. The session generated great interest among the attendees, which led to interesting discussions and many questions about the subject. Last Friday in the Sydney Oracle Meetup I talked about Oracle Flashback technology and how it helps to reduce downtime. Questions you always wanted to ask about Flashback Database…