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

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APPLIES TO:

Oracle Database – Enterprise Edition – Version 9.0.1.0 and later
Information in this document applies to any platform.

SYMPTOMS

 

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

CAUSE

There many possible reasons why a redo log file becomes corrupted.

SOLUTION

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. In this case, the database will have to be restored and recovered to a point in time to last available archivelog file.

NOTE: the ‘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.

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 specified logfile group.

IMPORTANT: It is essential that a new database backup is taken as missing archivelog sequence will affect full database recovery.

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