If you use identity columns in your database schema and want to make it possible for multiple users to take the solution offline, you must enable identity partitioning for your offline publications.
When designing tables in SQL Server, you have the option of enabling the Identity property for a column. Identities are incremented by SQL Server automatically as new rows are added, similar to an autonumber field in Access. If you do not use identity partitioning for your offline publications, two users who both take a team solution offline and add rows will have conflicting identities when they synchronize. Because other records may refer to this identity as a unique identifier, you do not want this number changed during synchronization.
By partitioning identities into large ranges for multiple users, the likelihood of conflicts is virtually eliminated.
To enable identity partitioning