Copy fails with “Error/Warning Detected: EXP-00056: ORACLE error 1555 encountered” (4299783)

The following errors are observed on the source copy log (the copy server log) when copy fails:

Thu Jan 13/20:01:17.066:: 003: Error/Warning Detected: EXP-00056: ORACLE error 1555 encountered

Thu Jan 13/20:01:17.070:: 003: ERROR: Stopping export thread - EXP-00056: ORACLE error 1555 encountered  at sync/svr/sync_export_thread.cpp:630

The Oracle error ORA-01555 has been encountered on source.

When copy runs into ORA-01555 on source, the following workaround can be tried to see if it can be run successfully again:

1. Run copy during quieter times.
2. Tune the rollback/undo segments as below: 

A. If using rollback segments, then create many large rollback segments, and make them all of the same size. Also, avoid the use of “OPTIMAL” parameter in rollback segments, or set it to a very high value if wanting to retain its usage. 

B. If using UNDO SEGMENTS rather than rollback segments, set the UNDO_RETENTION to a longer period of time than the copy is going to take. This may require trial and error approach.