Detect Database Corruption

**Check logical clause means that RMAN will check for logical corruption only.  If RMAN finds one or more data blocks are corrupted, it generates a trace and also listed in the v$database_block_corrupted. 

RMAN> run {

allocate channel d1 type disk;

allocate channel d4 type disk;

backup validate check logical database;

}

**The corrupted blocks are listed in the view v$database_block_corruption:

SQL> select * from v$database_block_corruption;

**The segment names are listed in the query below:

SELECT e.owner, e.segment_type, e.segment_name, e.partition_name, c.file#

, greatest(e.block_id, c.block#) corr_start_block#

, least(e.block_id+e.blocks-1, c.block#+c.blocks-1) corr_end_block#

, least(e.block_id+e.blocks-1, c.block#+c.blocks-1)

- greatest(e.block_id, c.block#) + 1 blocks_corrupted

, null description

FROM dba_extents e, v$database_block_corruption c

WHERE e.file_id = c.file#

AND e.block_id <= c.block# + c.blocks - 1

AND e.block_id + e.blocks - 1 >= c.block#

UNION

SELECT s.owner, s.segment_type, s.segment_name, s.partition_name, c.file#

, header_block corr_start_block#

, header_block corr_end_block#

, 1 blocks_corrupted

, 'Segment Header' description

FROM dba_segments s, v$database_block_corruption c

WHERE s.header_file = c.file#

AND s.header_block between c.block# and c.block# + c.blocks - 1

UNION

SELECT null owner, null segment_type, null segment_name, null partition_name, c.file#

, greatest(f.block_id, c.block#) corr_start_block#

, least(f.block_id+f.blocks-1, c.block#+c.blocks-1) corr_end_block#

, least(f.block_id+f.blocks-1, c.block#+c.blocks-1)

- greatest(f.block_id, c.block#) + 1 blocks_corrupted

, 'Free Block' description

FROM dba_free_space f, v$database_block_corruption c

WHERE f.file_id = c.file#

AND f.block_id <= c.block# + c.blocks - 1

AND f.block_id + f.blocks - 1 >= c.block#

order by file#, corr_start_block#;

* Check the corruption with the table and its index(s) to perform the cross reference

ANALYZE TABLE <OWNER.TABLE_NAME> VALIDATE STRUCTURE CASCADE;

* Validate all the datafiles in the database.

RMAN> backup validate database;

*  Run expdp/ export to detect any table level issues with all of the databases in a specific schema. 

*  DBVFY to check physical corruption