Undo tablespace is a kind of permanent tablespace used by oracle database engine to manage undo data if you are running your database in automatic undo management mode. This undo data or undo records are generally used to: Roll back transactions when a ROLLBACK statement is issued. Recover the database.

What happens if undo tablespace is full?

The UNDO tablespace works as follows: * The UNDO records are not deleted when they are expired. They stay and are overwritten only when a new UNDO record needs to be written and there is no free space. Thus, it is normal for UNDOTBS1 to appear at 99% full.

What is undo data in Oracle?

Oracle Database creates and manages information that is used to roll back, or undo, changes to the database. Such information consists of records of the actions of transactions, primarily before they are committed. These records are collectively referred to as undo.