Replicas and geodatabases

This topic applies to ArcEditor and ArcInfo only.

Geodatabase replication allows you to create copies of data across two or more geodatabases such that changes to the data may be synchronized.

Replica creation involves the user defining the data to replicate from a source geodatabase, then running a process to create replicas. The process copies data from the source geodatabase to a target geodatabase and creates a replica in each geodatabase. The replica describes what data has been replicated and contains the information needed to synchronize changes. The replica in the source geodatabase is the parent replica, and the replica in the target geodatabase is the child replica. Each combination of child and parent replicas is a replica pair. The term relative replica refers to the other replica in a replica pair.

The source must be an ArcSDE geodatabase, and therefore, parent replicas can only be hosted by ArcSDE geodatabases. You can also create multiple replicas from a single-source geodatabase. For example, you can create a replica for each county from your statewide enterprise geodatabase. The data involved in each replica may also overlap. The diagram below shows multiple replicas created from a single-source geodatabase.

An ArcSDE geodatabase can host both child and parent replicas. This enables data to be replicated across multiple geodatabases. The diagram below shows three ArcSDE geodatabases participating in replication. Initially, datasetA was in geodatabase1. A two-way replica was then created for datasetA using geodatabase1 as the source and geodatabase2 as the destination. Next, a second two-way replica was created for datasetA using geodatabase2 as the source and geodatabase3 as the destination. With these replicas in place, a change to datasetA in geodatabase3 can be applied to geodatabase2, which can then apply the change to geodatabase1. Since two-way replication is used, changes made in geodatabase1 can flow down to geodatabase3 in the same way.

It is also possible for a single ArcSDE geodatabase to host multiple child replicas. In this case, however, the datasets involved in each child replica must be distinct. For example, if a feature class named parcels is involved in one child replica, it cannot be involved in any other child replica in that geodatabase. The diagram below shows a single ArcSDE geodatabase hosting multiple child replicas, each referencing distinct datasets.

A personal or file geodatabase can be used as the target for a checkout or one-way replica. Personal and file geodatabases can also only host a single checkout or one-way replica at a time.