Health monitor runs the following checks:

• DB Structure Integrity Check—This check verifies the integrity of database files and reports failures if these files are inaccessible, corrupt or inconsistent. If the database is in mount or open mode, this check examines the log files and data files listed in the control file. If the database is in NOMOUNT mode, only the control file is checked.
   
• Data Block Integrity Check—This check detects disk image block corruptions such as checksum failures, head/tail mismatch, and logical inconsistencies within the block. Most corruptions can be repaired using Block Media Recovery. Corrupted block information is also captured in the V$DATABASE_BLOCK_CORRUPTION view. This check does not detect inter-block or inter-segment corruption.
   
• Redo Integrity Check—This check scans the contents of the redo log for accessibility and corruption, as well as the archive logs, if available. The Redo Integrity Check reports failures such as archive log or redo corruption.
   
• Undo Segment Integrity Check—This check finds logical undo corruptions. After locating an undo corruption, this check uses PMON and SMON to try to recover the corrupted transaction. If this recovery fails, then Health Monitor stores information about the corruption in V$CORRUPT_XID_LIST. Most undo corruptions can be resolved by forcing a commit.
   
• Transaction Integrity Check—This check is identical to the Undo Segment Integrity Check except that it checks only one specific transaction.
   
• Dictionary Integrity Check—This check examines the integrity of core dictionary objects, such as tab$ and col$. It performs the following operations:
   
  • Verifies the contents of dictionary entries for each dictionary object.
  • Performs a cross-row level check, which verifies that logical constraints on rows in the dictionary are enforced.
  • Performs an object relationship check, which verifies that parent-child relationships between dictionary objects are enforced.