Caché Installation Guide - InterSystems Documentation

Calculating System Parameters for OpenVMS
The nature of the application influences the appropriate number of buffers. If many users access a
small number of routines, a relatively small number of buffers will suffice for optimum response time.
Conversely, an application with a large number of routines will benefit from a large number of buffers.
The parameter calculator starts with a default value for the number of routine buffers. This default is
based upon a medium-sized site. You can enter a different value for this parameter in the Routine
Buffer Pool field in the parameter calculator based on the specifics of your site.
Note:
If you prefer to enter a value in this field with an MB unit of measure, this value is used for
the Memory for Routine Cache (MB) field in the Calculation Result section and also in calculations
involving routine buffers; it is not recalculated.
A.5.1.3 Determine Number of Global Buffers Per Process
The parameter calculator assumes the global buffers are 8 KB in size. The calculator starts with recommended
“rule of thumb” values for clustered and nonclustered systems.
If your system is memory-poor, you can reduce this value. Do not, however, decrease it below a multiple
of 32 KB per process.
Using more global buffers helps the performance of most sites. You can use the statistics produced by
the ^GLOSTAT utility to determine if adding more global buffers will reduce disk access and thereby
improve performance.
A.5.2 Record Current OpenVMS Parameter Values
Every system has memory needs other than those for Caché. For example, there are memory requirements
for computer language layered products as well as for OpenVMS itself. To analyze these
requirements for your system, use the following procedures to display the values of the indicated
parameters prior to installing Caché.
Note:
If you are performing an upgrade, shut down Caché to get accurate numbers.
1. Run the OpenVMS SYSGEN utility to display the current value of each parameter listed in the
OpenVMS System Parameter Values Table.
$ SET DEF SYS$SYSTEM
$ RUN SYSGEN
SYSGEN> USE CURRENT
SYSGEN> SHOW parameter-name
2. Run the OpenVMS SYSGEN utility to display the current value of the process parameters listed
in the OpenVMS Process Parameter Values Table.
$ SET DEF SYS$SYSTEM
$ RUN SYSGEN
SYSGEN> USE CURRENT
SYSGEN> SHOW/PQL
76 Caché Installation Guide