Repairing Corrupt Oracle Blocks Oracle Tips by Burleson

Advanced Oracle Utilities: The Definitive Reference by Rampant TechPress is written by top Oracle database experts (Bert Scalzo, Donald Burleson, and Steve Callan).  The following is an excerpt from the book.

Repairing Corrupt Blocks

The dbms_repair utility provides a mechanism to repair the corrupt database blocks, which is the fix_corrupt_blocks procedure.  Corrupt blocks are not really repaired, but instead are simply marked as corrupt.

Below is the syntax for the fix_corrupt_blocks procedure.  Note that the only OUT parameter is the fix_count.

• schema_name - The name of the schema containing the object with corrupt blocks.

• object_name – The name of the object needing repair.

• partition_name – The name of the partition or subpartition to process.  If none is specified and the object is partitioned, all partitions will be processed.

• object_type - Either table_object or index_object as specified as an enumeration.

• repair_table_name – The name of the repair table.

• flags – Not used.

• fix_count  – The number of blocks fixed.  This should equal the same number of corrupt blocks reported.

If the object repaired is a table, then any corresponding index also needs to be fixed.  The dump_orphan_keys procedure will indicate if any keys are broken.  If they are, the index will need to be rebuilt. 

Rebuilding Freelists

The dbms_repair utility provides a mechanism to rebuild the impacted freelists and bitmap entries after fixing block corruption.  This procedure recreates the header portion of the datafile, allowing Oracle to use the newly repaired blocks.

Below is the syntax for the rebuild_freelists procedure:

• schema_name – The name of the schema containing the object whose freelists need rebuilding.  

• partition_name – The name of the partition or subpartition whose freelists are to be rebuilt.

• object_type – Either TABLE_OBJECT or INDEX_OBJECT as specified as an enumeration.

Dbms_repair provides a new method of addressing ORA-600 errors dealing with block corruption.   The utility is very easy to use and very functional.  As described earlier, it is one of many potential solutions when resolving block corruption.  Dbms_repair does basically the same thing as analyze_table -validate structure.

Managing files on the Oracle server have been reviewed.  In the next section, the managing of user processes on the Oracle server will be detailed.

The Orakill Server Process Utility

In Windows, there are a couple of kill utilities: the Oracle-centric orakill utility and the Windows taskkill program.  The kill utilities should be used as a last resort only. If the session cannot be killed more gracefully via alter system kill session, or the instance is inaccessible via SQL, then orakill should be used to terminate the offending session.  Access to the Windows machine containing the database must be secure to use orakill. Any user with access to the box could access orakill or the Windows Task Manager and damage database processes. 

The Windows command to kill this session would be as follows:

In this example, the Windows thread corresponding to the Oracle session can be killed in the operating system without ever logging into the database. For another example, the Windows command to kill a session would be:

In this example, the thread (Oracle session) was killed in the operating system without ever logging into the database. Before killing the session, the DBA may decide to view the SQL being executed by the session. This can be obtained by using the TID above (300) in the following SQL statement:

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