Problem : ORA-01555: snapshot too old: rollback segment number 3 with name “_SYSSMU3$” too small

Problem : ORA-01555: snapshot too old: rollback segment number 3 with name “_SYSSMU3$” too small

I got following error.

EXP-00008: ORACLE error 1555 encountered
ORA-01555: snapshot too old: rollback segment number 3 with name “_SYSSMU3$” too small
EXP-00000: Export terminated unsuccessfully

My current undo_retention is 2500 sec, and undo tablespace is 3G.
Question:
– Do I need to change undo_retention or undo tablespace to fix the problem?
– How big should be?
– Does undo_retention need to be changed at downtime?

Thanks!


 

Solution: ORA-01555: snapshot too old: rollback segment number 3 with name “_SYSSMU3$” too small

Here’s an article to optimize your UNDO parameters
http://www.akadia.com/services/ora_optimize_undo.html