What is synchronization?

This topic applies to ArcEditor and ArcInfo only.

A synchronization involves one replica sending data changes and the relative replica receiving changes. Data changes include inserts, updates, and deletes made in the replica version. To perform a synchronization, you must be connected as the same database user as that used to create the replica, or the ArcSDE administrator.

For two-way and one-way replication, the filters and relationship class rules that were applied at creation are also applied to determine what changes to synchronize. Changes outside the filters and relationship class rules are not synchronized. See Replication and related data to see how to find the filters and relationship class rules for a replica. Logic is also used to prevent unnecessarily resending changes that have already been sent. For checkout replicas, all edits made to the checkout replica are synchronized.

Data transfer is based on exchanging replication messages. Message exchange between replicas is designed to be sequential. This means that the replicas are set up to exchange messages in a manner similar to the way voice messages are exchanged between parties engaged in a telephone conversation. Here each party sends a message to the other that is received and processed before the other party responds. The nature of the system ensures that only one replica can send changes at a time.

Geodatabase replication uses external messaging systems. Replication messages may be lost or received out of order due to errors in the network or other problems outside the geodatabase's management of the system. The geodatabase replication system is designed to detect and automatically recover from errors introduced by unreliable messaging.

Synchronization is supported in both a connected and a disconnected environment. In a connected environment, message exchange is handled by the system, while in a disconnected environment, you need to manage the message exchange. See connected synchronization and disconnected synchronization for more information.

During synchronization, changes are reconciled and posted into the replica version. During this reconcile, conflicts can occur. You can choose a reconcile policy to define how to handle these conflicts. You can also choose between column level and row level conflict detection for this reconcile. See synchronizing connected replicas and A quick tour of synchronizing disconnected replicas to see how to apply these options.