HP OpenVMS Systems Documentation

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The OpenVMS Frequently Asked Questions (FAQ)

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15.6.7 How can I split up an OpenVMS Cluster?

Review the VMScluster documentation, and the System Management documentation. The following are the key points, but are likely not the only things you will need to change.

OpenVMS Cluster support is directly integrated into the operating system, and there is no way to remove it. You can, however, remote site-specific tailoring that was added for a particular cluster configuration.

First: Create restorable image BACKUPs of each of the current system disks. If something gets messed up, you want a way to recover, right?

Create standalone BACKUP kits for the OpenVMS VAX systems, and create or acquire bootable BACKUP kits for the OpenVMS Alpha systems.

Use CLUSTER_CONFIG or CLUSTER_CONFIG_LAN to remove the various system roots and to shut off boot services and VMScluster settings.

Create as many architecture-specific copies of the system disks as required. Realize that the new systems will all likely be booting through root SYS0---if you have any system-specific files in any other roots, save them.

Relocate the copies of the VMScluster common files onto each of the new system disks.

Reset the console parameters and boot flags on each system for use on a standalone node.

Reset the VAXCLUSTER and NISCS_LOAD_PEA0 parameters to 0 in SYSGEN and in MODPARAMS.DAT.

Clobber the VMScluster group ID and password using SYSMAN.

Reboot the systems seperately, and run AUTOGEN on each.

Shut off MOP services via NCP or LANCP on the boot server nodes.

Permanent seperation also requires the duplication of shared files. For a list of the files commonly shared, please see Section 15.6.6.

Also see the topics on "cluster divorce" in the Ask The Wizard area.

For additional information on the OpenVMS Ask The Wizard (ATW) area and for a pointer to the available ATW Wizard.zip archive, please see Section 3.8.

Information on changing node names is included in Section 5.7.

15.6.8 Details on Volume Shadowing?

This section contains information on host-based volume shadowing; on the disk mirroring capabilities available within OpenVMS. Does volume shadowing require a non-zero allocation classes?

Yes, use of host-based Volume Shadowing requires that the disk(s) involved be configured in a non-zero allocation class.

Edit SYS$SYSTEM:MODPARAMS.DAT to include a declaration of an non-zero allocation class, such as setting the host allocation class to the value 7:


Then AUTOGEN the system, and reboot.

You should now be able to form the shadow set via a command such as the following:

$ MOUNT dsa1007: /SHADOW=($7$dkb300:,$7$dkb500:) volumelabel

When operating in an OpenVMS Cluster, this sequence will typically change the disk names from the SCSNODE prefix (scsnode$dkann) to the allocation-class prefix ($7$dkannn). This may provide you with the opportunity to move to a device-independent scheme using logical name constructs such as the DISK$volumelabel logical names in your startup and application environments; an opportunity to weed out physical device references.

Allocation class one is used by Fibre Channel devices; it can be best to use another non-zero allocation class even if Fibre Channel is not currently configured and not currently planned.

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