ORA-01555 : snapshot too old

ORA-01555 : snapshot too old : rollback segment number 60 with name

 This is because rollback records needed by a reader for consistent read are overwritten by other writers
This error normally occurs if you are running a very big transaction (like activating millions of records in an odds) and the redo log is to small. Try to enlarge the redo log and run your transaction again.

sql> show parameter undo_retention

 Increase Undo Table space to Auto Extended on.

1- increase the setting of UNDO_RETENTION:

 to change: SQL> alter system set undo_retention=(new-value)

2- increase the tablespace UNDO that contain the ROLLBACK segments

alter tablespace UNDO add datafile '(name-of-the-new-datafile)' size (size-value)M;