System Management Release Notes
4.36 Cluster Compatibility Patch Kits
Producers of such software can now modify their software using DDT Intercept
Establisher routines introduced in OpenVMS Alpha Version 7.3-2. For more
information about these routines, refer to the HP OpenVMS Alpha Version 7.3–2
New Features and Documentation Overview manual.
Note
If you are using a third-party disk-caching product or disk shadowing
application, refrain from using it in an OpenVMS SCSI or Fibre Channel
multipath configuration until you confirm that the application has been
revised using these new routines.
For more information about OpenVMS Alpha SCSI and Fibre Channel multipath
features, refer to Guidelines for OpenVMS Cluster Configurations.
4.36.3 DDT Intercept Establisher Routines and Device Configuration
Notification Results
V8.3
To ensure proper behavior of certain routines, a patch kit is required. Using those
routines without the required patch kit can result in system hangs, crashes, or
data corruption, and is not supported by HP.
For more information about these routines, see the HP OpenVMS Alpha Version
7.3–2 New Features and Documentation Overview manual.
4.36.4 Cluster Performance Reduced with CI-LAN Circuit Switching
V7.3-1
In rare cases, in an OpenVMS Cluster configuration with both CI and multiple
FDDI, 100 Mb/s or Gb/s Ethernet-based circuits, you might observe that
SCS connections are moving between CI and LAN circuits at intervals of
approximately 1 minute. This frequent circuit switching can result in reduced
cluster performance and may trigger mount verification of shadow set members.
PEdriver can detect and respond to LAN congestion that persists for a few
seconds. When it detects a significant delay increase or packet losses on a LAN
path, the PEdriver removes the path from use. When it detects that the path has
improved, it begins using it again.
Under marginal conditions, the additional load on a LAN path resulting from
its use for cluster traffic may cause its delay or packet losses to increase beyond
acceptable limits. When the cluster load is removed, the path might appear to be
sufficiently improved so that it will again come into use.
If a marginal LAN path’s contribution to the LAN circuit’s load class increases
the circuit’s load class above the CI’s load class value of 140 when the marginal
path is included (and, conversely, decreases the LAN circuit’s load class below
140 when the path is excluded), SCS connections will move between CI and LAN
circuits.
You can observe connections moving between LAN and CI circuits by using
SHOW CLUSTER with the CONNECTION and CIRCUITS classes added.
4–28 System Management Release Notes
