Question: I appear to have redo log corruption. When when I try
to start it it gives me the error:
ORA-01172: recovery of thread 1 stuck at block 25 of file 2
media recovery to recover block, restore backup if needed.
I think that the datafile that is corrupted is a redo log file, so is one of
the redo log groups that is with the status "current" even that the database
is in mount mode.
How do I repair redo log corruption?
Answer: First, followthese staps
attempt a simple startup/recovery.
Next, perform a full backup of what you have now,
before you proceed further.
Next, open a severity 1 service request
on MOSC. Check the oracle alert log & any trace files for more
details regarding your message and datafile.
If the database is up and redo logs are available you
could type RECOVER DATAFILE 2 and hit enter for now. If the database is
hung, SHUTDOWN IMMEDIATE then STARTUP MOUNT, then RECOVER DATAFILE 2, then
ALTER DATABASE OPEN. RECOVER DATABASE will check and recover all oracle
datafiles and is fine too.
Once you are working with MOSC, they will assist
you with techniques for
the corrupt data blocks.
When using undocumented parameters like
_allow_resetlogs_corruption, YOU MUST do it WITH the assistance of
Oracle tech support.
Oracle tech support may also be able to
patch the corrupt blocks
using the BBED utility.
Oracle Recovery with _allow_resetlogs_corruption
Recovery of a database using the undocumented parameter _allow_resetlogs_corruption
should be regarded as a last-ditch, emergency recovery scenario only, and
should not be attempted until all other avenues of recovery have been
Note that Oracle will not support a database that has
been recovered using this method unless it is subsequently exported and
Essentially, using _allow_resetlogs_corruption forces the
opening of the datafiles even if their SCNs do not match up; then, on the
next checkpoint, the old SCN values are overwritten. This could leave the
database in an unknown state as far as concurrency.
For additional information on handling corruption, see the
BC expert notes on corruption and see MOSC Note 1088018.1 - Handling
Oracle Database Corruption Issues.