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315Administering volume snapshots
Cascaded snapshots
Figure 9-6 Using a snapshot of a snapshot to restore a database
If you have configured snapshots in this way, you may wish to make one or more
of the snapshots into independent volumes. There are two
vxsnap commands
that you can use to do this:
■ vxsnap dis dissociates a snapshot volume and turns it into an independent
volume. The volume to be dissociated must have been fully synchronized
from its parent. If a snapshot volume has a child snapshot volume, the child
must also have been fully synchronized. If the command succeeds, the child
snapshot becomes a snapshot of the original volume. Figure 9-7 illustrates
the effect of applying this command to snapshots with and without
dependent snapshots.
Original
volume
vxsnap make source=V
Snapshot
volume of V:
vxsnap make source=S1
vxsnap restore V source=S2
Apply redo logs
1. Create instant snapshot S1 of volume V
2. Create instant snapshot S2 of S1
3. After contents of V have gone bad, apply the database redo logs to S2
4. Restore contents of V instantly from snapshot S2 and keep S1 as a stable copy
VS1
Original
volume
V
Snapshot
volume of V:
S1
Snapshot
volume of V:
S1
Snapshot
volume of V:
S1
Original
volume
V
Original
volume
V
Snapshot
volume of S1:
S2
Snapshot
volume of S1:
S2
Snapshot
volume of S1:
S2