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APRM® Technical Alert
# 002 |
Recommend System Value QPFRADJ be set to '2'.
| | Product: | APRM - V5R1M0 through V5R3M1 |
| | OS Level: | OS/400 - V5R1M0 and later |
| | Date: | December 1st, 2003, Modified April 15, 2005 |
Problem Summary
In a partitioned environment, it is possible that a partition may be powered-down
with an amount of main memory different from the amount it has when it is later
powered-up. This can result in poor performance or even a failed IPL unless
QPFRADJ is set to allow "Adjustment at IPL".
Background
The System Value QPFRADJ can have 4 values:
- 0 = No adjustment
- 1 = Adjustment at IPL
- 2 = Adjustment at IPL and automatic adjustment
- 3 = Automatic adjustment
For APRM to tune a partition at all, it is required that QPFRADJ be set to '2' or '3'
so that IBM's automatic process of moving memory between shared pools is active.
Issue
Changes of memory size are not frequent when done manually. When an automated
tuning tool such as APRM is installed memory sizes of partitions can and do get
changed more frequently. When a partition is powered-down, APRM will, subject
to the tuning rules established for it, remove memory as well as CPU power and
interactive performance so as not to waste these resources. When the partition
is later powered-up, APRM may restore some amount of resource (again, subject to
the tuning rules). There is, however, no record kept of how much the partition
had before it powered down since this is not relevant to the IPL-time workload.
The result is that it is likely that, when OS/400 gets control of the powering-up
partition, it will be at a different memory configuration than when OS/400 last had
control. If QPFRADJ is not set to allow adjustment at IPL, some memory pools
may be "starved" for resource.
Solution
QPFRADJ should be set to '2' for any partition where memory may be adjusted.
© Copyright 2003-2005 Barsa Consulting Group,
LLC. All rights reserved.