You might want to restructure a cascade to balance the load on your systems; to use a system or volume for a different purpose; or to perform upgrades, maintenance, or repairs.
About this task
For example, in the following cascade structure, you might want to make systemD:vol1
a destination of systemM:vol1
instead of a destination of systemC:vol1
The following diagram illustrates restructuring the relationship of the destinations in a cascade:
- On the destination system, change the /etc/snapmirror.conf file to indicate the new source for the destination.
systemM:vol1 systemD:vol1 - 35 * * 1,2,3,4,5
- As required, choose one of the actions from the following table.
|If the newest Snapshot copy on the destination...
|Exists on the source
||Use the following command to update the destination from the new source.snapmirror update -S source_volume dest_system:dest_volume
For example:snapmirror update -S systemM:vol1 systemD:vol1
|Does not exist on the source
||Perform one of the following tasks.
- Update the new source from the original source using the snapmirror update command. Wait for the destination to update.
- Make the destination writable using the snapmirror break command. Then resynchronize the destination with the new source using the snapmirror resync command.
- Release the former source using the following command:snapmirror release source_volume [[dest_system:]dest_volume]
systemC> snapmirror release systemC:vol1 systemD:vol1
Disconnecting a destination from a cascading series
The following diagram depicts the change in the SnapMirror cascade configuration:
For the configuration depicted in the preceding diagram, suppose that from systemB you enter the following command:snapmirror release vol1 systemC:vol1
These results follow.
- systemA:vol1 continues to be the source for the destination systemB:vol1.
- systemC:vol1 no longer copies from systemB:vol1. SnapMirror retains Snapshot copies for systemC and below.
- If systemC requests an update from systemB, the destination is reestablished if it is still not writable and the base Snapshot copy still exists on the source.
- systemD:vol1 still copies systemC:vol1.
- All the destinations that depend on systemL:vol1 continue functioning as before.
You can check that the destination was released by running the snapmirror destinations command on systemA, as follows.
systemA> snapmirror destinations -s systemA:vol1
Volume Snapshot Destination
vol1 systemB(0015269532)_vol1.37 systemB:vol1
vol1 systemL(0015269532)_vol1.42 systemL:vol1->systemM:vol1->systemXvol1->systemY:vol1
vol1 systemL(0015269532)_vol1.42 systemL:vol1->systemM:vol1->systemXvol1->systemZ:vol1
vol1 systemL(0015269532)_vol1.42 systemL:vol1->systemM:vol1->systemN:vol1
Note: If you want to permanently release a destination, you should delete the entry in the /etc/snapmirror.conf file. Alternatively, you can comment out the entry by preceding it with a pound sign (#). Otherwise, SnapMirror attempts to update the destination.