Appendix: Using the In-Band Control Messaging Utility vxibc and the IBC Programming API

This appendix explains how to use the IBC Messaging command-line utility vxibc and the API for off-host processing. The In-Band Control (IBC) Messaging feature with the Snapshot feature of Volume Replicator (VVR) and optional FastResync (FR) feature of Volume Manager (VxVM) enable you to perform off-host processing. Typically, to perform off-host processing, you would use the vradmin ibc command to sequence and automate the operations. For more information, see Chapter 6, Using VVR for Off-Host Processing. However, if you want to customize the process beyond what can be achieved by using the vradmin ibc scripts, or if you want to program and integrate off-host processing in your control facility, you need to use the vxibc command or the IBC API.

Off-host processing consists of performing operations on application data on a host other than the one where the application is running. Typical applications include Decision Support Systems (DSS), backup, and trial failover in VVR. In a VVR environment, off-host processing reduces the load on the application server, the Primary, and uses the potentially under-utilized Secondary.

The model for data access on the Secondary is that you break off a mirror from each data volume in the RVG, perform the operation on the mirror, and then reattach the mirror while replication is in progress.