HP Volume Shadowing for OpenVMS |
Creating and Managing Shadow Sets with System... |
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Using $DISMOU to Dismount Shadow Sets
The call to the $DISMOU system service has the following format:SYS$DISMOU devnam, flags
The action that $DISMOU takes depends in part on whether you specify a shadow set virtual unit or a shadow set member in the devnam argument.
For a complete description of the $DISMOU service and its arguments, refer to the HP OpenVMS System Services Reference Manual.
Removing Members from Shadow Sets ![]()
If you want to remove a single member from a shadow set, you
must make a call to $DISMOU. In the devnam argument,
you should specify the name of the shadow set member you want to
remove. The specified member is spun down unless you specify the
DMT$M_NOUNLOAD option in the flags argument.
The MACRO-32 code in Removing a Member from a Shadow Set demonstrates a call to $DISMOU that removes the member $2$DUA9 from a shadow set.
| Example 4 Removing a Member from a Shadow Set |
$DMTDEF FLAGS: .LONG DMT$M_NOUNLOAD MEMBER001: .ASCID /$2$DUA9:/ . . . $DISMOU_S - devnam = MEMBER001, - flags = FLAGS . . . .END |
Dismounting and Dissolving Shadow Sets ![]()
If you want to dismount a shadow set on a single node, you
must make a call to $DISMOU. In the devnam argument,
you should specify the name of the virtual unit that represents
the shadow set you want to dismount. If you want to dismount the
shadow set clusterwide, specify the DMT$M_CLUSTER option in the flags argument of the call.
When you dismount a shadow set on a single node in an OpenVMS Cluster system, and other nodes in the OpenVMS Cluster still have the shadow set mounted, none of the shadow set members contained in the shadow set are spun down, even if you have not specified the DMT$M_NOUNLOAD flag. After this call completes, the shadow set is unavailable on the node from which the call was made. The shadow set is still available to other nodes in the cluster that have the shadow set mounted.
If the node on which the shadow set is being dismounted is the only node that has the shadow set mounted, the shadow set dissolves. The shadow set member devices are spun down unless you specify the DMT$M_NOUNLOAD flag.
The MACRO-32 code in Dismounting and Dissolving a Shadow Set Locally demonstrates how to use the $DISMOU system service to dismount the shadow set represented by the virtual unit DSA23.
| Example 5 Dismounting and Dissolving a Shadow Set Locally |
$DMTDEF FLAGS: .LONG 0 DSA23: .ASCID /DSA23:/ . . . $DISMOU_S - devnam = DSA23, - flags = FLAGS . . . .END |
When a shadow set is dissolved:
The MACRO-32 code in Dismounting and Dissolving a Shadow Set Across the Cluster demonstrates a call to the $DISMOU system service to perform a dismount across the cluster. When the shadow set is dismounted from the last node, the shadow set is dissolved.
| Example 6 Dismounting and Dissolving a Shadow Set Across the Cluster |
$DMTDEF FLAGS: .LONG DMT$M_CLUSTER DSA23: .ASCID /DSA23:/ . . . $DISMOU_S - devnam = DSA23, - flags = FLAGS . . . .END |
You must specify the DMT$M_CLUSTER option with the flags argument if you want the shadow set dismounted from every node in the cluster. When each node in the cluster has dismounted the shadow set (the number of hosts having the shadow set mounted reaches zero), the volume shadowing software dissolves the shadow set.
Setting $DISMOU Flags for Shadow Set Operations ![]()
$DISMOU Flag Options lists
the options for the $DISMOU flags argument
and describes the shadow set operations that use these options.
For a full description of each of these flag options, refer to the
description of the $DISMOU service in the HP OpenVMS System Services
Reference Manual.
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