Automatic Undo Management (AUM)

If you have installed an 11g database for this exercise, then AUM is the default method of Undo Management. With earlier versions of Oracle, Manual Undo Management was the only method available. DBAs needed to be good at the balancing act of managing rollback segments for different tasks in the database—batch jobs, data loads, smaller online transactions, and so on.

Identifying data in undo segments by flashing back to timestamp

There is a small trick in identifying data that may still exist in the undo segments. This won't work if the undo has already been overwritten, so it is best used when you are alerted to the mistake quickly. I have eliminated the possibility of flashback technology being involved by disabling it with the following commands (flashback is not required for this exercise):

SYS@NEWDB> SHUTDOWN IMMEDIATE;
SYS@NEWDB> STARTUP MOUNT;
SYS@NEWDB> ALTER DATABASE FLASHBACK OFF;
SYS@NEWDB> ALTER DATABASE OPEN;
SYS@NEWDB> show parameter...