Problem or error: Errors occur during a contact process cell execution as follows.

Solution: The rollback segment keeps undo information for the transaction. This is needed for read consistency. A Select statement does not cause a rollback to be held. As soon as the transaction that generated the rollback commits, that rollback may be overwritten by another query. With a long-running Select query, the earlier rollback segments may be overwritten to the extent that the Oracle database cannot produce a result consistent with the start of the query.