UNDO SQL refers to SQL that reverses transactions. UNDO and REDO transaction recoveries are application recoveries where the effects of specific transactions during a specified timeframe are removed from the database. Specific transactions are recovered to a state as opposed to a particular point in time. These types of transaction recovery methods provide users with the capability to selectively repair specific parts of a tablespace. The database is offline during recovery.
Users then run or rerun batch programs to restore valid work.
UNDO - Users can apply UNDO SQL to remove only the bad transactions. The database can remain online during this procedure. Valid work is not lost. The second step to this procedure restores good transactions through the application of REDO SQL . To avoid the high cost in personnel, time and machine resources of a manual transaction recovery process, a robust transaction recovery solution is needed.