Re: rbs oracle data block corrupted

[Tim Gorman]

Atul,   Using "_OFFLINE_ROLLBACK_SEGMENTS" or "_CORRUPTED_ROLLBACK_SEGMENTS" might allow you to open the database, but there is an almost absolute certainty that you will hopelessly corrupt the data in the database in doing so.  So this is not a solution, this is the absolute very LAST resort.   Instead, using these parameters usually means that you will be initiating a complete dump all of the data out of this database in order to load it into a "fresh" new uncorrupted one.  Please do NOT consider using these parameters unless you've exhausted all other possibilities, and absolutely do NOT use them without logging a SEV-1 TAR and having an Oracle Support analyst on the phone throughout.   The danger of these parameters is that just about everyone has heard about them, but very few clearly understand how they work and the implications.  Roughly put, the "_OFFLINE_ROLLBACK_SEGMENTS" parameter means that Oracle will attempt to determine whether the transaction has been committed or rolled back.  If it can, it will put things right.  If it can't, Oracle will just simply commit the transaction.  Of course, it may have been that the transaction was never committed, thus corruption.  Roughly, the "_CORRUPTED_ROLLBACK_SEGMENTS" parameter means that the rollback segment in question is hopeless, and Oracle will simply commit any uncommitted transaction that were using it.  Again, this is very scary...   ---   The best solution to data block corruption?   Data block corruption should first be treated exactly like media failure.  That is, exactly like a failed disk drive.  Restore an older copy of the datafile from a backup that occurred prior to the detection of the corruption, and recover forward until a complete recovery has been performed.   But first, before doing even that, please verify that the database block indicated is really corrupt.  The ALTER SYSTEM DUMP DATAFILE <file#> BLOCK <block#> command will make a symbolic dump of the block to a ".trc" file in your USER_DUMP_DEST directory.  The error message has the "file#" and "block#" values in it, so please use those then examine the resulting ".trc" file.  If it truly is corrupt, there will some obvious indication the ".trc" file (i.e. it'll say "corrupted").   Then, please backup the datafile in question before restoring over it, just out of caution.  Or, if you know how, rename the datafile and restore it from backup to the new location.  Either way, don't wipe out the datafile with the corruption if you can help it...   Hope this helps...   -Tim ----- Original Message ----- From: Nikunj Gupta To: Multiple recipients of list ORACLE-L Sent: Saturday, June 29, 2002 4:23 PM Subject: Re: rbs oracle data block corrupted In Init.ora there is some setting to ignore using ROLLBACK Segments. Talk to Oracle support and try that.   ------------------------------------ Make a FREE long distance call from your PC! http://www.eboom.com/free/ ----- Original Message ----- From: Danisment Gazi Unal (ubTools) To: Multiple recipients of list ORACLE-L Sent: Saturday, June 29, 2002 11:43 AM Subject: Re: rbs oracle data block corrupted Hi, which version of Oracle are you using ? what are the all error messages ? regards... Atul Kumar Srivastav wrote:  Hi All ! We have one problem. We can mount the database but not able to open it. It gives following error while opening: One Oracle Data Block Corrupted. RBS01.dbf (datafile for rollback segment) How can i repair this corruption? Atul -- Danisment Gazi Unal http://www.ubTools.com