ORA-01555: snapshot too old: rollback segment number 56 with name "_SYSSMU56_782841858$" too small

Hello Team,

Daily schedule job from target oracle cloud use to import couple of schemas from ORACLE 11gR2  to down stream(through DBlink with expdp on oracle procedure which is configured on target oracle cloud DB), now after upgraded the source DB into oracle 12C R2, same schemas with quite few new tables for the same import job  is failing with following / mentioned error.

ORA-01555: snapshot too old: rollback segment number 56 with name "_SYSSMU56_782841858$" too small

Hope if I need to overcome above issue, do I need to increase retention period on source DB or target DB ??.. else is there any other good way to resolve the issue, since the issue is in production, if it can be done without any parameter change which will be great for me.