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>The UB and the UP entries are generated from the same database instruction,
>which is why they are guaranteed to hit the *JRNRCV in a 1,2 sequence.

I'm not doubting that this is true, just confused by it. A "database
instruction" is still made up of mutiple RISC opcodes, no? On a pre-emptive
multi-tasking system like OS/400 it's possible for a job to be swaped out at
any time, no? Therefore, even on a uni-processor why is this a guarentee?
Not to mention the fact that on a multi-processor   two jobs could truly be
running at the same time.

Now, I could see this being true if all db updates in the system were
actually funneled through a single thread or mutex, but that seems like a
bottleneck, no?

-Walden

------------
Walden H Leverich III
President
Tech Software
(516) 627-3800 x11
(208) 692-3308 eFax
WaldenL@xxxxxxxxxxxxxxx
http://www.TechSoftInc.com 

Quiquid latine dictum sit altum viditur.
(Whatever is said in Latin seems profound.)
 

-----Original Message-----
From: Al Barsa [mailto:barsa@xxxxxxxxxxxxxxxxxxx] 
Sent: Friday, September 05, 2003 10:06 AM
To: Midrange Systems Technical Discussion
Subject: Re: Are journal's UB & UP entries guaranteed to be in 1-2 sequence?







The UB and the UP entries are generated from the same database instruction,
which is why they are guaranteed to hit the *JRNRCV in a 1,2 sequence.

Al - unsure if I like being a fish for a week on Orlando

Al Barsa, Jr.
Barsa Consulting Group, LLC

400>390

914-251-1234
914-251-9406 fax

http://www.barsaconsulting.com
http://www.taatool.com



                                                                           
             G Armour                                                      
             <garmour400m@yaho                                             
             o.com>                                                     To 
             Sent by:                  Midrange Systems Technical          
             midrange-l-bounce         Discussion                          
             s+barsa2=attgloba         <midrange-l@xxxxxxxxxxxx>           
             l.net@xxxxxxxxxxx                                          cc 
             m                                                             
                                                                   Subject 
                                       Re: Are journal's UB & UP entries   
             09/05/2003 09:30          guaranteed to be in 1-2 sequence?   
             AM                                                            
                                                                           
                                                                           
             Please respond to                                             
             Midrange Systems                                              
                 Technical                                                 
                Discussion                                                 
             <midrange-l@midra                                             
                 nge.com>                                                  
                                                                           
                                                                           




I was going to ask for documentation references, but if Al says it...

BTW, Al, did you mean to say "precede"?

Actually, I presumed that a UB would always precede a UP, but my bigger
question is whether there was a possibility of an interceding entry
between the UB & UP entries for the same database record.  If I had 1000
users in the same program that were updating 1000 different records (1
each per user) in the same file, and they all hit the Enter key to update
the record at the same time, will IBM guarantee that I won't encounter a
scenario like:

Journal
Sequence#  Type   Record's Key
   201      UB    AAAAAAAAAAA      (From user Joe)
   202      UB    BBBBBBBBBBB      (From user Fred)
   203      UP    AAAAAAAAAAA      (From user Joe)
   204      UP    BBBBBBBBBBB      (From user Fred)

This example shows that there is an interceding UB entry (202) between the
UB & UP entries for the record with key AAAAAAAAAAA.  If this is possible,
I need to build an array of UB entries in my RCVJRNE exit program, and
Look-Up that array whenever I process a UP entry so that I can compare the
changes made to the record.

Obviously, I would rather not have to deal with such an array in this
program, but if I can't be sure that the above scenario will never happen,
then I'll need to.

Advice & suggestions welcomed.

GA

--- Al Barsa <barsa@xxxxxxxxxxxxxxxxxxx> wrote:
> You are absolutely guaranteed that a UB will immediately proceed a UP.
>
> Al
>
> Al Barsa, Jr.
> Barsa Consulting Group, LLC
>
> 400>390
>
> 914-251-1234
> 914-251-9406 fax
>
> http://www.barsaconsulting.com
> http://www.taatool.com
>
>
> From G Armour: garmour400m@xxxxxxxxx>
>
> Are an update record's UB (Update Before) & UP (Update After) entries
> guaranteed (no quibble, rock-solid, cross-my-heart) to be in 1-2
> sequence,
> with NO possibility of another entry being written between them?  I
> could
> not find any reference to this in the manuals, and so I must now presume
> the possibility exists and must store the UB entries in an array,
> waiting
> for the UP entry to arrive and match to the UB entry by JOCTRR (the
> RRN)?
> Since the program is RETURNed without setting LR on after each entry is
> processed, the UB entries will still remain in the array on subsequent
> calls to the program, correct?
>
> I am writing an exit program to a RCVJRNE command.  I need to compare
> before & after images on an update to a record to determine if I need to
> take a specific action.  The files being journaled are getting both the
> before & after images journaled.
>
> Also, as I now see that the exit program is RETURNed without LR on after
> *each* journal entry, doesn't that have the potential to be a resource
> drain?
>
> TIA, GA


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