104 - [Oracle 19C] Categories of Undo

 

 

 

Active

Uncommitted undo information

required if a user wants to roll back or if the transaction has failed. 

Uncommitted undo information is never overwritten.

 

 

Unexpired

Committed undo information

Old undo information with an age that is less than the current undo retention period retained for consistent read and  Oracle Flashback operations

 

 

Expired

Expired undo information

Old (committed) undo information that is older than the current undo retention period is said to be expired and its space is available to be overwritten by new transactions.