WSC IBM Z
|Abstract: Several instances have been encountered recently regarding anomalies in CPU performance data reported by RMF and similar performance monitors. |
|The symptoms are as follows:
- LPAR Management time on behalf of the partition is reported as ‘****’ on the RMF Partition Data Report.
- LPAR Busy and MVS Busy are not in sync, with MVS Busy consistently being reported as higher than LPAR busy, and the processor is not reported as 100% busy, (or close to 100% busy), on the RMF Partition Data Report, (Physical Processors Total).
- Increased LPAR Management time, with some installations reporting as high as 10% LPAR management time, even with only 1 dominant partition active on the processor.
LPAR Management Time is time spent by the LPAR hipervisor on behalf of the partition, (Partition Management Time), and on behalf of the total configuration, (*PHYSICAL* Management Time), and is a reflection of both the workload activity within the partition(s) and the total configuration managed by the hipervisor.
Generally LPAR Management Time includes time spent managing the different partitions, including the dispatching of physical processors to logical processors, enforcement of partition weights, and updating System Activity Display, (SAD), information. Other functions, however, can result in increased LPAR Management Time. Among these functions are the use of certain instructions, such as Store CPU ID, (STIDP), and Store Subchannel Id, (STSCH).
Computer Associates’(*) product CA-ASTEX(*) uses the Store Subchannel Id, (STSCH), instruction to obtain information on ESCON Director Port busy time. Customer’s using the CA-ASTEX product, with this featured enabled, can expect to see any or all of the above described symptoms.
Informational APAR II12131 will be created, documenting the above described symptoms, and will provide information on the fix number to be requested from Computer Associates to address the use of the Store Subchannel instruction. Customers operating in an LPAR environment and experiencing the above described symptoms, are urged to review the informational APAR and apply the documented fix to the CA-ASTEX product.
(*) Computer Associates and CA-ASTEX are registered trademarks of Computer Associates.
IBM System z Family
OS/390, Performance, 096836, LPAR, PR/SM
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