[11gR2]: ORA-12801: error signaled in parallel query server Pxxx & ORA-01555: snapshot too old: roll
I have implemented parallelism in Oracle 11gr2 by using following commands at session-level
execute immediate 'alter session set PARALLEL_DEGREE_POLICY=AUTO';
execute immediate 'alter session force PARALLEL QUERY';
but this error is encountered:
ERROR: ORACLE execute error: ORA-12801: error signaled in parallel query server P015
ORA-01555: snapshot too old: rollback segment number string with name "string" too small
I have increased UNDO_RETENTION from 900 to 2400 but error still remain ... why ?
Thanks for help.
GD.