Compaq COBOL AAQ2G1FTK User Manual
Page 35
Developing Compaq COBOL Programs
1.1 Compaq COBOL and Alpha Architecture System Resources
More physical memory can also be made available to a process (if it is present
on the machine) by adjusting the system generation parameter WSMAX and
the corresponding WSEXTENT (in AUTHORIZE). Approach such adjustments
with great caution, as the system may hang if memory is oversubscribed and you
create a situation where OpenVMS Alpha effectively has no options to reclaim
memory. The following guidelines can help:
•
Set the COBOL user WSEXTENT (in AUTHORIZE or INITIALIZE/QUEUE)
to match WSMAX.
•
Keep WSQUOTA (in AUTHORIZE or INITIALIZE/QUEUE) low. Make sure
that no process or batch queue has a WSQUOTA of more than approximately
20% of physical memory. The difference between WSEXTENT and WSQUOTA
allows OpenVMS Alpha to manage memory to meet varying demands.
•
Use AUTOGEN. AUTOGEN will attempt to make a consistent set of changes
that do not interfere with each other.
By default, AUTOGEN will set the maximum working set (system generation
parameter WSMAX) to 25% of physical memory. This value is reasonable for
a workstation or multi-user system with many active processes.
WSMAX can be increased to a somewhat larger value by editing
MODPARAMS.DAT. For a system with 64 MB
1
of physical memory, set
WSMAX to no more than approximately 40% of physical memory, or 52000
pagelets (1 MB = 2048 pagelets). With 128 MB or more of physical memory, a
setting of 50% of physical memory can be attempted.
The effects of physical memory on compilation time were studied for a set of
seven large modules. These modules ranged in size from approximately 1600 to
3300 disk blocks. Your results may differ, but to give a rough appreciation for the
effect of physical memory on compilation time, note that:
•
When the amount of physical memory available to the processes matched the
amount of virtual memory, the elapsed times were close to the CPU times.
•
As the physical memory was reduced, CPU times rose only slightly—
approximately 10%.
•
As the physical memory was reduced, elapsed times were elongated, at the
rate of approximately 1 hour for each 100 MB of difference between Peak
Virtual Size and the actual memory available. For example, when compiling
a program that used a Peak Virtual Size of 947760 pagelets, or 463 MB, on
a system where approximately 180 MB of physical memory was available to
user processes, the compile required approximately 3 hours more than on a
512 MB system.
Your results may differ from those shown in this section and will be strongly
affected by the speed of the devices that are used for paging.
Note that the requirements for virtual memory and physical memory can also be
reduced by breaking large modules into smaller modules.
1
MB= megabytes
Developing Compaq COBOL Programs 1–5