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In-Band Control Messaging overview

When you take a snapshot on the Secondary, it contains a point-in-time copy of the data on the Primary. Because the Secondary may be behind the Primary, it is not known at exactly what time this point-in-time copy was made.

IBC messaging enables you to send a message in the replication stream to notify the Secondary that an event has occurred on the Primary. In the case of a file system, you can use the sync command on the Primary, and then send an IBC message. When this message arrives on the Secondary, the data on the Secondary is consistent at the file system level and replication stops. You then split off a mirror, which now contains a consistent image of the file system, and unfreeze replication.

The model with IBC Messaging is that a process on the Secondary waits for the IBC Message, and a process on the Primary sends the message when the desired event has occurred.

VVR provides the following options for IBC Messaging:

• Single command to perform off-host processing operations—vradmin ibc

  This chapter explains the function of IBC Messaging and how to use the command vradmin ibc for off-host processing.

• IBC Messaging command-line utility—The vxibc utility

  For more information on how to use the command-line utility vxibc, see Using the In-band Control Messaging utility vxibc and the IBC programming API.