Oracle Solution for Error ora-03170

ORA-03170: deadlocked on readable physical standby (undo segment string)

What triggered the Error:

A new undo segment was added. A query can occasionally deadlock when issued around the time an undo segment is added and used immediately on the primary.

What should we do to fix it:

Retry the query. Avoid creating new undo segments when using standby as a regular part of operation.