20 points to anyone who is old enough to remember *why* we couldn't rely on the 
Locked clause.





-----Original Message-----
From: Charles Stevenson <stevenson.c...@gmail.com>
To: Paul Wilson <sfr192...@yahoo.com>; U2 Users List 
<u2-users@listserver.u2ug.org>
Sent: Mon, Oct 24, 2011 5:28 pm
Subject: Re: [U2] [UV] LIST.READU EVERY's "waiters" when there are writes w/o 
explicit readu.


Come to think of it, I think customizing CSC's MHC s/w was the 1st time 
 ever fought this fight.
Before that, I had always programmed under a standard that demanded a 
EADU before a WRITE.   And every READU needed a LOCKED clause.
cds
On 10/24/2011 6:57 PM, Paul Wilson wrote:
 That little company called CSC does/did not use readu's - they put login id in 
ield 1 and used that for a 'locking' situation.



 ________________________________
 From: "Woodward, Bob"<bob_woodw...@k2sports.com>
 To: U2 Users List<u2-users@listserver.u2ug.org>
 Sent: Monday, October 24, 2011 7:06 PM
 Subject: Re: [U2] [UV] LIST.READU EVERY's "waiters" when there are writes w/o 
xplicit readu.

 Oh I agree!  I was just thinking round-robin that if we're going to talk
 about adding a LOCKED clause to the WRITE statement, matching the
 structure of READU, then we ought to have a WRITEU, too.  Didn't say I
 liked the idea....

 -----Original Message-----
 From: u2-users-boun...@listserver.u2ug.org
 [mailto:u2-users-boun...@listserver.u2ug.org] On Behalf Of Mecki
 Foerthmann
 Sent: Monday, October 24, 2011 3:30 PM
 To: u2-users@listserver.u2ug.org
 Subject: Re: [U2] [UV] LIST.READU EVERY's "waiters" when there are
 writes w/o explicit readu.

 Now why would anybody want to use a WRITE without a READU?
 I can possibly understand that somebody would want to do it with a
 WRITEV (i.e writing a flag on a record) but WRITE?
 And WRITE totally ignoring locking would be outright stupid.

 On 24/10/2011 22:28, Woodward, Bob wrote:
> I would think that because you are not trying to obtain the lock in a
> WRITE statement, it would not be classified as a waiter.  True, it's
> waiting because of the lock but by not trying to obtain the lock, it's
> only waiting for the blockage to clear.  If it were to be classified
 as
> a waiter then I would expect to see a LOCKED clause on the WRITE
> statement like there is on the READU.  For that matter, I'd expect to
> see a WRITEU command as well and the standard WRITE to completely
 ignore
> locking.
>
> Just my guess, though.
>
> BobW
>
> -----Original Message-----
> From: u2-users-boun...@listserver.u2ug.org
> [mailto:u2-users-boun...@listserver.u2ug.org] On Behalf Of Charles
> Stevenson
> Sent: Monday, October 24, 2011 2:12 PM
> To: U2 Users List
> Subject: [U2] [UV] LIST.READU EVERY's "waiters" when there are writes
> w/o explicit readu.
>
> UV 10.2.10 on Windows is behaving differently from what I recall.
> Are my expectations out of line?
>
> Suppose Session A holds a readu lock; and Session B attempts a WRITE
 to
> same record withOUT!!! 1st explicitly getting the readu lock.
> Session B waits for Session A to release the lock before writing the
> record.
>
> While Session B is waiting,  does it show up as a "waiter" in
 LIST.READU
> EVERY?
> I expected so,  but it doesn't.
>
>
> Session A                       Session B
> _____________________________   ___________________
> 1A. ED VOC DUMMY
>        (this sets the readu lock.)
>
> 2A. (stay in editor)            2B. run this:
>                                         01:    OPEN 'VOC' TO F ELSE
 STOPM
> 'nope'
>                                         02: ***READU REC FROM F, 'DUMMY'
> ELSE NULL
>                                         03:    WRITE '' TO F, 'DUMMY'
>
> 3A. Within ED:
>         XEQ LIST.READU EVERY
>
>
> If I UN-comment line 2, LIST.READU EVERY shows something like this:
>
>         Active Read Waiters:      Owner   Waiter
>         Device....  Inode....     Userno  Userno
>         746117947    232860913      6116    3396
>
>
> But when I comment out line 2, LIST.READU is silent.
> I have not yet explored what the deadlock daemon does.
>
> TIA,
> cds
>
>
> P.S. Yes, yes, "Bad Form", "Legacy Software", 20 min wait is
> configurable, . . . we can talk later.
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