Weird spike in System time every 5:00 minutes...

From: Don Whitlow (dwhitlow1_at_wi.rr.com)
Date: 08/28/03 

Date: 28 Aug 2003 14:35:47 -0700

Hi All,

I have what I consider to be an odd behavior on some of my AIX boxes.
So far, on most of the AIX servers I have that are running Sybase, I
see a brief spike every 5 minutes in system time, either via sar, or
through topas. In general, the spikes go up to anywhere between 20 and
40% and last for only a couple seconds. However, the 'weird' part is
that it is just about always on the '5's, meaning 12:00, 12:05, 12:10,
etc. etc... See sar output below:

16:09:44 %usr %sys %wio %idle
16:00:45 25 6 1 67
16:00:46 20 6 0 73
16:00:47 26 6 2 67
16:00:48 32 13 2 54
16:00:49 17 13 7 62
16:00:51 32 27 7 34
16:00:52 29 47 17 7
16:00:53 22 46 14 17
16:00:54 40 23 3 34
16:00:55 38 14 0 47

I realize this could be something Sybase is doing every 5 minutes, but
our DBAs can't find or think of anything that would sync itself to
happening not only at given intervals, but set times as well. I
figured I would put this out to the group just to see if maybe AIX
does something every 5 minutes. Maybe process cleanup, memory
reclamation, fs io cache writeouts, or something like that?

It might not be anything to worry about. At this point I think it's
more of a curiosity. But, any thoughts on what it may be would be
appreciated.

Thanks,
Don

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