On 2016-02-25 09:34, Ed Jaffe wrote:
I brought this up on IBM-MAIN many years ago after noticing several
system traces, from large customers, with less than one screen's worth
of good trace data. At that time, the maximum trace table size was 999K
and I recommended setting that size (if you could afford the real
memory). 1M is now the default...
Just last night I was asked to take a look at a dump -- from a large
customer running on the newest, biggest "iron" -- that had only .045
seconds of good trace data:
******** Trace data is not available from all processors before this time.
0008 0269 008C3448 I/O 02013 00000000_0D91ABCA 10104007 6F932740
0C000100 00000080 00000000 0009 0269 08:22:55.743019140 40
07544000 80000000 024FE070
00100000 00000000
.
. (two measly pages of trace data)
.
0012 0226 084B8B00 SSRV 118 A6476E64 01E6A110 8007611A
08245B88 Suspend 08:22:55.788338762 6E
00000000
******** Trace data is not available from all processors after this time.
Don't forget to re-visit your MVS trace table allocations whenever you
upgrade your hardware. Luckily, major increases in processor speed and
the number of logical processors have been accompanied by similar
increases in LPAR real memory allocations, making larger trace tables
possible.
The TRACE ST command now supports up to 9G per processor! LOL! I'm not
in any way suggesting that value be used, I'm just pointing out that
it's possible.
IMHO, trace tables should be sized to hold _at least_ one full clock
second of data on your zIIPs or whatever your fastest processors might
be. Others might have different ROTs.
Just do it! Your debugging teams will thank you. :)
Too bad listservs don't have "like" buttons!
I can't count the number of times where key information was outside of
the time range covered by system trace. On the other side of the coin, I
can think of several cases where the trace table size was a generous
size and information I needed was several seconds before the event
causing the dump.
Providing ample storage for system trace is a great way to help your
vendors solve any problems you encounter, and in today's environment of
cheap and plentiful storage the cost is minimal.
--
Regards, Gord Tomlin
Action Software International
(a division of Mazda Computer Corporation)
Tel: (905) 470-7113, Fax: (905) 470-6507
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