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Oracle AUM tips

Oracle Database Tips by Donald BurlesonMarch 1, 2015

Question:  What is Oracle's automatic undo management (AUM) and how to I use it on my database?

Answer:  Oracle automatic undo management was introduced to relieve the DBA tedium of sizing undo to remove the ORA-01555 snapshot too old error.  With AUM, Oracle manages the size of the rollback segments (later re-named undo logs) to ensure that DML-intensive transactions can complete successfully.

See my notes here on using Oracle AUM.

Automatic unto management is set by default in 11g (via the undo_management=auto parameter), but you can migrate to automatic undo in earlier releases that support AUM by creating an undo tablespace and set undo_management=auto and bounce your database: 

create undo tablespace
size 2m reuse autoextend on; 

alter system set undo_tablespace=ts_undo; 

alter system set undo_management=auto;



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