ORA-01555: snapshot too old during datapump export

Datapump Export can fail with the following error when the parameter FLASHBACK_TIME is used

ORA-31693: Table data object "SCOTT"."EMPLOYEES" failed to load/unload and is being skipped due to error: ORA-02354: error in exporting/importing data ORA-01555: snapshot too old: rollback segment number 271 with name "_SYSSMU271$" too small ORA-00604: error occurred at recursive SQL level 3 ORA-08180: no snapshot found based on specified time ORA-06512: at "SYS.TIMESTAMP_TO_SCN", line 1^@ ORA-00604: error occurred at recursive SQL level 3 ORA-08180: no snapshot found based on specified ti

The reason for this is the database parameter UNDO_RETENTION is set to low compared to the time set with FLASHBACK_TIME.

Example:

- export starts at 10:00 pm and ends at 00:00 am. Flashback time start at 10:00 pm of the same days when export starts.

Expdp may need 2 hours to complete and undo_retention is set to 2040 that means 34 minutes. So the information in undo is recycled.

Solution
Set UNDO_RETENTION to a value sufficient to get all info required by the flashback time.
Also consider increasing undo tablespace size.