ORA-01555 can be avoided by following precautions:

ORA-01555 can be avoided by following precautions:

1. Database should be in Automatic Undo Management mode.
2. Use a large optimal value for undo_retention.
3. Use a large optimal size of rollback segment (undo) size.
4. Should avoid to fetch (select / cursors) between commits.
5. Should Commit less often at the time of long running query, to reduce Undo Segment slot reuse.
6. Try to run long running queries on off peak hours, when there is less DML transactions on database.