Please read here: http://oratips-ddf.blogspot.com/2008/02/dreaded-ora-01555.html David Fitzjarrell ________________________________ From: dba1 mcc <mccdba1@xxxxxxxxx> To: Oracle-L@xxxxxxxxxxxxx Sent: Tue, March 16, 2010 7:48:49 AM Subject: wield ORA-01555 error??? we have ORACLE 10.2.0.4 on UNIX system. Recently one of our databases has ORA-0155 error happen several times. this database already setup: 1. undo_retention = 20000 2. undo data file size current is 9 GB and can autoextend to 25 GB how come we still get ORA-01555 error? Thanks. -- //www.freelists.org/webpage/oracle-l