Couldn't the owner of the program just put a statement in the title
and thus eliminating the whole issue?
Ed
On Nov 13, 2012, at 4:04 PM, John Gilmore wrote:
Bill Fairchild writes:
<begin extract>
Only those who have studied the code that accesses the ULUT can know
exactly how safe it is to use the ULUT without first serializing.
<end extract>
and thus makes my point better than I did. In this OCO period we
cannot know. We must therefore assume that accessing a dynamic list,
q
On 11/13/12, Bill Fairchild <bfairch...@rocketsoftware.com> wrote:
If your code is only reading from a control block structure and
you do not
serialize, there is the danger that other code might serialize and
update
the control block structure in a way that could cause your code to
behave
incorrectly. I do not know the structure or use of the UCB lookup
table
(ULUT) as used now in z/OS. But I remember the lookup table
scheme in MVT
and the queue of UCBs that we used to have in between MVT and z/
OS. The
other code might change the UCB that you have found and are
reading-only, in
which case your code needs to withstand the possibility that any
or all of
the fields may change while you are looking at it. Possibly a UCB
might be
deleted, in which case even a lookup table can not prevent your
code's
attempting to accessing freshly FREEMAINed storage. Perhaps even
the entire
ULUT could be freed and replaced with a whole new ULUT at a different
virtual address. Only those who have studied the code that
accesses the
ULUT can know exactly how safe it is to use the ULUT without first
serializing.
Bill Fairchild
Programmer
Rocket Software
408 Chamberlain Park Lane * Franklin, TN 37069-2526 * USA
t: +1.617.614.4503 * e: bfairch...@rocketsoftware.com * w:
www.rocketsoftware.com
-----Original Message-----
From: IBM Mainframe Discussion List [mailto:IBM-
m...@listserv.ua.edu] On
Behalf Of John Gilmore
Sent: Tuesday, November 13, 2012 3:38 PM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: "New" way to do UCB lookups
Jim Mulder's point is very well taken indeed.
Traversing a dynamic list without serialization on the assumption
that since
you do not plan to change it no one else will is a mug's game.
John Gilmore, Ashland, MA 01721 - USA
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John Gilmore, Ashland, MA 01721 - USA
t.
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