This appendix explains how to use the IBC Messaging command-line utility vxibc and the API for off-host processing. You can use the In-Band Control (IBC) Messaging feature with the FastResync (FMR) feature of Veritas Volume Manager (VxVM) and its integration with VVR to take application-consistent snapshots at the replicated volume group (RVG) level. This lets you perform off-host processing on the Secondary host. Typically, to perform off-host processing, you would use the vradmin ibc command to sequence and automate the operations.
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.
You can use any of the snapshots (mirror break-off, full instant snapshot, or the space saving instant snapshot) to create a point in time (PIT) image of the RVG volumes on the Secondary site for off-host processing. You can use the IBC mechanism to make sure that the snapshots taken on the Secondary site are application-consistent. You can then refresh the snapshots or reattach them using fast resynchronization.