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Chapter 6. Performance Considerations 417
1st ed., 6/30/04 - 312579601
Define High Dispatching Priority for the HSC
The VM dispatch priority and SHARE settings of the ACS service machine may be altered
to improve overall HSC performance for a VM host system.
Set High-Performance Host-to-Host Communications
In a multi-host ACS configuration, host-to-host communications allows hosts to notify
each other of a CDS switch. Host-to-host communications can be accommodated through
three performance levels of communications, ranked as follows:
•ACF/VTAM
•the LMU(s)
•the CDS.
The high-performance telecommunications method is through VTAM. This method is
recommended by StorageTek. Host-to-host communications through the control data set
should be used only as a backup facility. You should implement the highest level of
host-to-host communications available.
‘‘Communication Functions’’ and ‘‘Communications Path (COMMPath) Command and
Control Statement’’ in the HSC Operator’s Guide describe how multiple hosts are
connected by any of the three possible communication methods. You have the capability
to set or dynamically switch the host-to-host communication method between each pair of
hosts. You can monitor the level of communication using the Display COMMPath
command. If a level of communications fails, it automatically drops to the next lower
level, allowing the HSC to continue without interruption.
The communications parameters can be modified dynamically, using the COMMPath
command, without halting HSC execution.
Detailed Information about Host-to-Host Communications
Refer to “Communication Functions” on page 78 and to ‘‘Communications Path
(COMMPath) Command and Control Statement’’ in the HSC Operator’s Guide for a
general description of communication functions.
Refer to “PARMLIB Control Statements” on page 83 for how to define communication
functions in a PARMLIB control statement.
The HSC Operator’s Guide contains information about the operator commands for
controlling the host-to-host communication path.