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What are the redo log files that are no longer required for instance recovery known as?
Redo log files that are no longer required for instance recovery are called inactive redo log files. If you have enabled archiving (the database is in ARCHIVELOG mode), then the database cannot reuse or overwrite an active online log file until one of the archiver background processes (ARCn) has archived its contents.
How do I drop an unused redo log group?
You can drop a redo log group only if it is inactive. If you need to drop the current group, first force a log switch to occur. Make sure a redo log group is archived (if archiving is enabled) before dropping it. To see whether this has happened, use the V$LOG view.
What is the difference between archive log and redo log?
Archive logs are archived redo(online) log files. In redo log files are all changes that happened to your data. If your database is in archivelog mode, than redo logs can’t be overwritten, they are archived in some other location when they are full. Redo and archive logs are used in various database recovery scenarios.
When to clear an inactive redo log group?
You can clear an inactive redo log group when the database is open or closed. The procedure depends on whether the damaged group has been archived. Reinitialize the damaged log group. Clearing a not-yet-archived redo log allows it to be reused without archiving it.
What happens if a redo log file is lost?
Assuming the case for an env. where there are 3 REDO log groups with 2 members in each group. In such a case if one member of one group is lost, the database would continue to be running as its able to write on the other member of this group but would throw the error in the Alert log and the STATUS of the lost member would become INVALID.
How to recover from loss of online redo log and ora-312?
ALTER DATABASE CLEAR UNARCHIVED LOGFILE GROUP 2; If there is an offline datafile that requires the cleared log to bring it online, then the keywords UNRECOVERABLE DATAFILE are required. The datafile and its entire tablespace have to be dropped because the redo necessary to bring it online is being cleared, and there is no copy of it.
What happens when all members of a redo group are lost?
When all the members of a REDO group are lost, the database would crash, in fact SMON would kill itself causing the shutdown as there is no place to write the REDO, which in turn means no recovery of transaction thus Oracle shuts itself to make sure no more transactions are committed when it cannot write the same to the redo logs.
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