OpenVMS Cluster Systems - OpenVMS Systems - HP

Preparing a Shared Environment
5.4 Clusterwide Logical Names
$ DEFINE/TABLE=new-clusterwide-logical-name-table logical-name -
_$ equivalence-string
Note
If you attempt to create a new clusterwide logical name with the same
access mode and identical equivalence names and attributes as an
existing clusterwide logical name, the existing name is not deleted, and
no messages are sent to remote nodes. This behavior differs from similar
attempts for other types of logical names, which delete the existing name
and create the new one. For clusterwide logical names, this difference is
a performance enhancement.
The condition value SS$_NORMAL is returned. The service completed
successfully, but the new logical name was not created.
5.4.6 Management Guidelines
When using clusterwide logical names, observe the following guidelines:
1. Do not use certain logical names clusterwide.
The following logical names are not valid for clusterwide use:
• Mailbox names, because mailbox devices are local to a node.
• SYS$NODE and SYS$NODE_FULLNAME must be in LNM$SYSTEM_
TABLE and are node specific.
• LMF$LICENSE_TABLE.
2. Do not redefine LNM$SYSTEM.
LNM$SYSTEM is now defined as LNM$SYSTEM_TABLE,
LNM$SYSCLUSTER_TABLE. Do not reverse the order of these two
tables. If you do, then any names created using the /SYSTEM qualifier or in
LNM$SYSTEM would go in LNM$SYSCLUSTER_TABLE and be clusterwide.
Various system failures would result. For example, the MOUNT/SYSTEM
command would attempt to create a clusterwide logical name for a mounted
volume, which would result in an error.
3. Keep LNM$SYSTEM contents in LNM$SYSTEM.
Do not merge the logical names in LNM$SYSTEM into LNM$SYSCLUSTER.
Many system logical names in LNM$SYSTEM contain system roots and
either node-specific devices, or node-specific directories, or both.
4. Adopt naming conventions for logical names used at your site.
To avoid confusion and name conflicts, develop one naming convention for
system-specific logical names and another for clusterwide logical names.
5. Avoid using the dollar sign ($) in your own site’s logical names, because
OpenVMS software uses it in its names.
6. Be aware that clusterwide logical name operations will stall when the
clusterwide logical name database is not consistent.
This can occur during system initialization when the system’s clusterwide
logical name database is not completely initialized. It can also occur when the
cluster server process has not finished updating the clusterwide logical name
database, or during resynchronization after nodes enter or leave the cluster.
5–10 Preparing a Shared Environment