RMF/SMF SYNC parameter for MICS
Article ID: 51126
Updated On:
Products
Issue/Introduction
Specification of the RMF Monitor SYNC Parameter
Environment
Component: MRMF
Resolution
Specification of the RMF Monitor SYNC Parameter
The RMF Monitor SYNC(nn) parameter may be used to specify whether or not RMF intervals are to be synchronized with the hour of the day, and, if so, the number of minutes after the hour when synchronization is to occur. The synchronization is accomplished by shortening the first RMF interval so that a subsequent interval within the first hour begins nn minutes after the hour in which RMF is started. If the requested length of the RMF interval is evenly divisible into 60 minutes, all subsequent intervals will be synchronized.
For example, if INTERVAL(30) and SYNC(00) are specified and RMF is started at 07:05, then the first interval will start immediately and it will end at 07:30, for a duration of 25 minutes rather than the 30 minutes requested. This shortening will result in the second interval starting at 07:30, the requested synchronization point. The ending timestamp (ENDTS) for each RMF record written to SMF at the
end of an interval will be at 30 minutes after the hour and on the hour.
In CA MICS, DETAIL RMF data may be summarized, not into the hour in which the measured activity took place but into the following hour, because the product summarizes by HOUR and ZONE, both of which are derived from ENDTS. In the above example, data that were collected by RMF between 07:30 and 08:00 will have an ENDTS of 08:00:00.00 or possibly a few seconds later due to internal delays. The HOUR value for this interval is 8, even though most of the measurements represent information for the previous hour.
Specifying SYNC(59) and using an INTERVAL value that is evenly divisible into 60 solves this problem. As a result of the SYNC(59), no more than the last minute of the last interval within an hour is summarized into the next hour, instead of the entire last interval. The margin of error has been reduced from INTERVAL minutes to 1 minute.
Instead of the RMF synchronization with the hour, if you use the synchronization with SMF, with the SYNC(SMF) parameter, RMF records will be written as specified via SYNCVAL and INTVAL general SMF options.
Therefore, the CA MICS recommendation for RMF synchronization is:
- RMF synchronization only: (SYS1.PARMLIB(ERBRMFxx))
- RMF options:
SYNC(RMF,59M)
INTERVAL(nn) where nn can be 05, 10, 12, 15, 20, 30 or 60
- RMF options:
- RMF synchronization with SMF recording: (SYS1.PARMLIB(SMFPRMxx))
- RMF options:
SYNC(SMF)
(INTERVAL value is ignored) - SMF options:
SYNCVAL(59)
INTVAL(nn) where nn can be 05, 10, 12, 15, 20, 30 or 60
- RMF options:
For more information on SYNC and related RMF options, see the IBM manual Resource Measurement Facility (RMF) User's Guide.
Additional Information
We do, however, STRONGLY recommend that the RMF SYNCVALvalue be set to 59. This is because of MICS summarization--and the fact that MICS uses the ENDTS (End timestamp) value to determine MICS common data elements like HOUR.
If you were to use a an RMF SYNCVAL value of 00, for example, and 15 minute interval records, for the 8 a.m.hour, you would have intervals that ended at 8:15, 8:30, 8:45, and 9:00. These four intervals logically contain the data for hour 8. In the MICS DETAIL timespan records, there would be no problem--each record would contain 15 minutes of data.
The problem occurs when we summarize to the MICS DAYS timespan---in this case, the data in the DAYS timespan for hour 8 would NOT contain the last interval above, because we use ENDTS, and the last interval ended at 9:00--so the hour value would be 9--not 8.
The DAYS timespan record for hour 8 would actually contain data from 7:45 to 8:45 (because the interval starting at 7:45 ended at 8:00 a.m. (hour 8).
That is why it is very important to use a SYNCVAL of 59---this means that with 15 minute intervals, you would have intervals ending at 8:14, 8:29, 8:44, and 8:59---(where the 1st interval started at 7:59 (almost 8)).
So--with SYNCVAL 59, MICS interval records summarized to the DAYS timespan are only off by 1 minute off from truly representing the HOUR specified in the DAYS database records. (basically 7:59 - 8:59 is the actual data).
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