I was going to reply to this earlier but didn't remember all the facts.
Mike reminded me of some of it. This was discussed on the list a year or
3 ago. Mike is right about cylinders being partially filled and that
will show a cylinder as being used whether it has 1 page on it or is
completely full. It seems to me that the response from one query command
will show the number of cylinders with "anything" on them regardless how
full and the response from another query command shows the percent of
pages in the direct area that are filled. I don't remember which
commands however. They must be QUERY ALLOC with MAP or DRCT, unless
there is another QUERY command.
Jim
clifford jackson wrote:
Thanks Mike for your quick response....
From: Mike Walter <[EMAIL PROTECTED]>
Reply-To: The IBM z/VM Operating System <IBMVM@LISTSERV.UARK.EDU>
To: IBMVM@LISTSERV.UARK.EDU
Subject: Re: DRCT area question
Date: Thu, 20 Sep 2007 14:30:01 -0500
Clifford,
I only answer because no one from Endicott has yet.
The DRCT cyls contain the "object" (or "compiled") form of the source
directory. Over time, updates to the DRCT space cause fragmentation of
the space. VM:Secure (and probably DIRMAINT, and maybe even DIRECTXA)
will, when needed, reorganize the space (VM:Secure calls it a directory
REBUILD).
That reorganization consolidates small directory entries on large cylinder
spaces so that fragments are moved to fill whole cylinders, leaving other
whole completely cylinders free. That might explain why you see such a
dramatic change in allocated DRCT extents.
BTW, it's a "best practice" to over-allocate the DRCT space. Since it
won't "commit" changes until everything has been successfully written to
disk, it needs at least as much space to reorganize as it is using. I try
to ensure that we never get beyond about 40% full. Disk is cheap compared
to down time when increasing DRCT cyls in a crisis. The DRCT *can* be
increase on the fly, but very few people could do it without spending "a
while" with their head in manuals - and even then are not sure until they
try it on a test system. Plan ahead.
Mike Walter
Hewitt Associates
Any opinions expressed herein are mine alone and do not necessarily
represent the opinions or policies of Hewitt Associates.
"clifford jackson" <[EMAIL PROTECTED]>
Sent by: "The IBM z/VM Operating System" <IBMVM@LISTSERV.UARK.EDU>
09/20/2007 12:19 PM
Please respond to
"The IBM z/VM Operating System" <IBMVM@LISTSERV.UARK.EDU>
To
IBMVM@LISTSERV.UARK.EDU
cc
Subject
DRCT area question
Over the past few days I've done a 'q alloc drct' the % use has changed
from
45% to 50% and now to 15% what is this telling me
q alloc drct
EXTENT EXTENT %
VOLID RDEV START END TOTAL IN USE HIGH USED
------ ---- ---------- ---------- ------ ------ ------ ----
510RES 1000 1 20 20 3 3 15% ACTIVE
------ ------ ----
SUMMARY 20 3 15% CKD
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