Remember when looking at SMF volume, record counts are interesting, but the 
bigger issue is the number of bytes written. 

We (Peter Enrico and myself) recommend collecting at least 99 subtypes 6, 10, 
11, 12, and 14. 

6 is especially important as it's the summary service class period information 
(every 10 seconds)
10 is dynamic processor speed changes, which you hopefully don't see
11 is for Group Capacity limits, and is written every 5 minutes
12 is HiperDispatch interval (2 second) data which can show you utilization 
information on a 2 second basis which can be quite interesting
14 is HiperDispatch topology data written every 5 minutes or when a change 

The 6s and 12s are in fact high volume in terms of the number of records, but 
the records themselves are relatively short. In terms of bytes, from what I've 
seen the subtype 6 is somewhere between 40 and 100 MB of additional SMF data 
per system per day. Subtype 12 seems to run around 40 to 50MB. I expect that's 
not noticeable in most environments. Indeed, the type 30s can easily be more 
data than that. Not to mention the 101s, 110s, and 120s. I actually have a 
slide on this in an upcoming conference presentation. 

The other 99 subtypes are used less often and some can be more voluminous than 
the 6 summary records. If you don't want to record those subtypes all the time, 
I'm ok with that. But OTOH, if you need them to do a deep dive on WLM to try to 
understand why things worked the way they did, then having them handy is better 
than having to turn them on and recreate the issue. We don't formally recommend 
people keep them enabled, but if it was me, I'd probably keep at least most of 
them enabled. 

The 92s are file system information. The subtypes 10 and 11 are written every 
time a file is opened/closed. In large Websphere Application Server 
environments I've seen these being very voluminous. I haven't looked at them 
lately, but my recollection from quite some time ago is that directory 
traversal (at least in the HFS file systems) triggered these records as well. 
I've seen the 92s in such an environment being much more voluminous than the 
99s. In that environment, I did have the 92s turned off because of this.

There are relatively new subtypes (at least 50-59) in the 92s, that may be why 
the OP is seeing more 92s. It looks like possibly useful information if you're 
tuning zFS performance, but I personally haven't spent any time yet 
investigating them. 

Scott Chapman

On Thu, 8 Feb 2018 16:17:47 +0000, Allan Staller <> wrote:

>Not sure about SMF92, but SMF99 are "WLM decision records".
>Yes they are large volume, but somewhat indispensable.
>Generally when there is a WLM problem it is extremely difficult or impossible 
>to reproduce.
>If the SMF99's are not available "during the problem" it is virtually 
>impossible to debug.
>IMO, SMF99's should be recorded.  I know Cheryl Watson and others may disagree.
>My US$ $0.02 worth,

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