Disconnect time can also show up as synchronous remote copy (SRDF). If the
links are saturated it will elongate the DISC time and therefore the RT.
Joel Wolpert
Performance and Capacity Planning consultant
WEBSITE: www.perfconsultant.com
----- Original Message -----
From: "Ron Hawkins" <[email protected]>
Newsgroups: bit.listserv.ibm-main
To: <[email protected]>
Sent: Thursday, July 29, 2010 11:59 AM
Subject: Re: Any ROT for DASD Response time
J,
This is what Pat describes as "SIBLING PEND" and it is easy to spot the
symptom because it shows up as Disconnect Time.
I sure IBM and EMC have something like HDS's Performance Monitor. It's a
GUI
with exportable data that you can use to monitor skewed activity across
the
parity groups that lead to the elongated seek affect that you describe.
Ron
-----Original Message-----
From: IBM Mainframe Discussion List [mailto:[email protected]] On
Behalf Of
J Ellis
Sent: Thursday, July 29, 2010 4:47 AM
To: [email protected]
Subject: Re: [IBM-MAIN] Any ROT for DASD Response time
also, as some very wise people on this list and other lists/papers have
pointed out "Know thy data" some of our worst dasd response time issues
were
eliminated by simply looking at the logical volume placement and the data
sets there on. Moving some DB2 indexes into different array groups and/or
off logical volumes that were splattered out towards the middle of the
small
spinning back end dasd can make a great deal of difference (know your
chunk
sizes, how the chunks are spread across the disks in the arrays, etc...).
RAID technology (at least yet) doesn't make up for bad placement of
storage
group volumes and the data sets on them. As others pointed out, research
Dr.
Artis papers on the subject--just my opinion and experience.
(Because we've always done it this way *BANG*)---Running HSM migration
management/space release-along with compactor jobs on different lpar in
the
plex- on logical volumes that were on the front of the disks in the
arrays
absolutely killed the hot indexes that were in the middle of the disks in
the same array.
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