If you plan to replicate your database, you need to consider what field size is appropriate for the AutoNumber field used as a table's primary key. If you use an AutoNumber field as the primary key for a table in the replicated database, set its FieldSize property to either Long Integer or Replication ID.
If fewer than 100 records are routinely added between synchronizingreplicas, use a Long Integer setting for the FieldSize property to take up less disk space.
If more than 100 records are routinely added between synchronizing replicas, you should use Replication ID for the FieldSize property setting to prevent records from being assigned the same primary key value in each replica. Note, however, that an AutoNumber field with a Replication ID field size produces a 128-bit value that will require more disk space.