Veritas Volume Manager 5.0.1 Administrator's Guide, HP-UX 11i v3, First Edition, November 2009

DMP tunable parameters
Table 16-2 shows the DMP parameters that can be tuned by using the vxdmpadm
settune command.
Table 16-2
DMP parameters that are tunable
DescriptionParameter
If this parameter is set to on, the first open of a device that
is performed by an array support library (ASL) is cached.
This caching enhances the performance of device discovery
by minimizing the overhead that is caused by subsequent
opens by ASLs. If this parameter is set to off, caching is
not performed.
During Dynamic Reconfiguration (DR) operations, the
dmp_cache_open tunable needs to be turned on.
The default value is off.
dmp_cache_open
The number of kernel threads that are available for servicing
path error handling, path restoration, and other DMP
administrative tasks.
The default number of threads is 10.
dmp_daemon_count
How long DMP should wait before retrying I/O after an array
fails over to a standby path. Some disk arrays are not capable
of accepting I/O requests immediately after failover.
The default value is 15 seconds.
dmp_delayq_interval
If this parameter is set to on, it enables the path restoration
thread to be started.
See “Configuring DMP path restoration policies” on page 189.
If this parameter is set to off, it disables the path
restoration thread. If the path restoration thread is currently
running, use the vxdmpadm stop restore command to
stop the process.
See “Stopping the DMP path restoration thread” on page 191.
dmp_enable_restore
Performance monitoring and tuning
Tuning VxVM
540