The SnapMirror policy for the relationship defines the contents of the baseline and any updates.

A baseline transfer under the default vault policy XDPDefault makes a Snapshot copy of the source volume, then transfers that copy and the data blocks it references to the destination volume. Unlike SnapMirror relationships, a vault backup does not include older Snapshot copies in the baseline.

Updates are asynchronous, following the schedule you configure. The rules you define in the policy for the relationship identify which new Snapshot copies to include in updates and how many copies to retain. The labels defined in the policy (“monthly,” for example) must match one or more labels defined in the Snapshot policy on the source. Otherwise, replication fails.

At each update under the XDPDefault policy, SnapMirror transfers Snapshot copies that have been made since the last update, provided they have labels matching the labels defined in the policy rules. In the following output from the snapmirror policy show command for the XDPDefault policy, note the following: