The update mode specifies whether a record’s potential duplicate list is reevaluated when key fields are updated in the record. Performing the reevaluation helps keep the potential duplicate list current, but requires more system resources.
There are two update modes.
Pessimistic – In this mode, a record’s potential duplicates are reevaluated whenever updates are made to the record’s key fields. Key fields are fields involved in blocking and matching.
Optimistic – In this mode, potential duplicates are not reevaluated when key fields are updated in a record. After an update, the potential duplicate list for a record remains the same as before the update occurred.