Problem- ORA-01555 snapshot too old error

Impact: It affects read consistency of oracle.
Solution:

The ORA-01555 snapshot too old error can be addressed by several remedies:

1.  Re-schedule long-running queries when the system has less DML load.
2. Increasing size of rollback segments.  The ORA-01555 snapshot too old also relates to your setting for automatic undo retention
3. Don't fetch between commits.