Chapter 6 Synchronizing Replicas

This chapter describes the process of synchronization. Synchronization uses the same export-transport-import procedure that is used during replica creation:

• Export phase-At one site, a syncreplica (synchronize replica) command is invoked with the -export option. This creates a packet of data.

• Transport phase-The packet is sent to one or more other sites.

• Import phase-At the other sites, a syncreplica command is invoked with the -import option. This applies the changes in the packet to an existing replica.

The syncreplica command is optimized for performance; it creates a packet that contains only the information required to update the target replicas specified on the command line.

Figure 19 illustrates the MultiSite replica-synchronization scheme. At Site 1, a syncreplica -export command places version data and records of operations from replica1 into a packet. The packet is sent to Site 2. At Site 2, a syncreplica -import command imports the contents of the packet into replica2. Note that each synchronization is one-way. If two replicas update each other, two synchronizations are required.

Figure 19 Replica Synchronization