Technical data

Setting Up and Maintaining Queues
14.6 Using Queue Options
Process Limit Description
Working set quota The value that approximates the amount of physical memory used
by each batch job in the queue in a memory-constrained system.
Working set extent The value that approximates the amount of physical memory in a
memory-rich system.
You should set this to a high value. The working set extent value
is an upper limit for the size of the working set; the working set
cannot be expanded beyond this value even if more memory is
required by the job. If you set this value too low, a job might
page fault heavily even if the system has plenty of memory
available. To be safe, choose a working set extent value equal
to the system parameter value of WSMAX, which specifies the
maximum working set size possible for your system.
In general, the working set quota and extent values specified in the UAF record
for each user are sufficient. However, you can specify more generous or stringent
values for a queue, depending on the purpose of the queue. For example, you
can encourage users to submit large jobs (such as compiling and linking large
programs) as batch jobs to reserve interactive use of the system for jobs that do
not require extensive resources, as follows:
• Set a large working set size for batch jobs by specifying larger WSQUOTA
and WSEXTENT values when you create the batch queue.
• Restrict the working set size of interactive jobs by providing smaller
WSQUOTA and WSEXTENT values in users’ UAF records.
14.6.4.4 CPU Default and Maximum
You can restrict and expand the amount of time a job is allowed in the CPU by
setting CPU limit values.
Do not set CPU time limit values too low. When a job’s CPU time limit is
exceeded, the job is terminated with an error status. If working set values
(explained in Section 14.6.4.3) are set too low, the system might use memory
less efficiently but the jobs can still complete normally. However, if CPU time
limit values are set too low, the system might terminate jobs that are making
legitimate and authorized use of the CPU.
For example, you might use a CPU time limit on a batch queue devoted to
execution of newly coded software that could unexpectedly enter a CPU loop. The
CPU time limit would terminate infinitely looping jobs so they do not waste the
CPU resource. However, you must be careful to choose a sufficiently high time
limit so normally executing jobs do not terminate prematurely.
Another way to control allocation of the CPU resource is to create a special-
purpose batch queue that shifts execution of its jobs to a less busy time of day
when CPU time is more available.
14.6.4.5 Swapping
Typically, swapping is enabled on batch queues. However, for a special-purpose,
high-priority queue, you might disable swapping. This provides a favorable status
to jobs in this queue by removing them from consideration when memory must be
reclaimed from processes (through the operating system’s swapping and trimming
mechanism).
For more information, refer to the OpenVMS Performance Management.
14–34 Setting Up and Maintaining Queues