ORA-01555: Snapshot too old : rollback segment number XXX with name NNN too small.

Cause: Rollback records needed by a reader for consistent read are overwritten by other writers

Action: If in Automatic Undo Management mode, increase undo_retention setting. Otherwise, use larger rollback segments

 

select rb.segment_name, rs.optsize, rs.hwmsize
from v$rollstat rs, dba_rollback_segs rb where rs.usn = rb.segment_id;

alter rollback segment rbs0 storage (optimal 100m);

alter system set undo_retention=10800;