Oracle REDO LOG CORRUPTION - DROPPING REDO LOGS NOT POSSIBLE - CLEAR LOGFILE

Posted by PDSERVICE on Nov 18, 2015 In

Oracle REDO LOG CORRUPTION - DROPPING REDO LOGS NOT POSSIBLE - CLEAR LOGFILE

Problem Description:

====================

- Redo log corruption errors in one of the redo log files while the database is open.

The redo log corruption could be any of these errors:

ORA-16038 log %s sequence# %s cannot be archived

ORA-354 corrupt redo log block header

ORA-353 log corruption near block <num> change <str >time <str>

ORA-367 checksum error in log file header

ORA-368 checksum error in redo log block

- Dropping the redo logs is not possible as it may be needed for instance recovery.

- The online redo logs may not be dropped if:

+ There are only two log groups

+ The corrupt redo log file belongs to the current group

Solution Description:

=====================

- Clear the logfile having the problem:

Syntax:

alter database clear <unarchived> logfile group <integer>;

alter database clear <unarchived> logfile '<filename>';

eg: alter database clear logfile group 1;

alter database clear unarchived logfile group 1;

- An online redo log file with status=CURRENT or status=ACTIVE in v$log may not be cleared and

the error ORA-1624 will be produced.

- Please note that 'alter database clear logfile' should be used cautiously. If no archived log was produced, then

a complete recovery will not be possible. Perform a backup immediately after completing this command.

Solution Explanation:

=====================

- If an online redo log file has been corrupted while the database is open,

the 'alter database clear logfile' command can be used to clear the files

without the database having to be shutdown.

- The command erases all data in the logfile.

IMPORTANT: It is wise to take a fresh backup.

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