Re: File that has records constantly being added and deleted

I am at V4R5 and this is true for this release.  So, it has been around 
for a while.

Nick

Nick Radich
Sr. Programmer/Analyst
EPC Molding, Inc.
Direct  (320) 679-6683
Toll free  (800) 388-2155  ext. 6683
Fax  (320) 679-4516
nick_radich@xxxxxxxxxxxxxx



"mlazarus@xxxxxxxxxxxxx" <mlazarus@xxxxxxxxxxxxx> 
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Re: File that has records constantly being added and deleted






Rich,

 This is not really true anymore.  Check out the CRTDTAQ command.  There's
a new parameter:

                  Automatic reclaim (AUTORCL) - Help 
 
Specifies whether the storage allocated for the data queue is 
automatically reclaimed (released) when the data queue is empty. 

 Another enhancement is that the maximum size is 2GB, up from 16MB.

 -mark

Original Message:
-----------------
From: Rich Loeber rich@xxxxxxxxx
Date: Tue, 26 Sep 2006 08:13:36 -0400
To: midrange-l@xxxxxxxxxxxx
Subject: Re: File that has records constantly being added and deleted


A word of warning about using a data queue.  Space management on data
queues is
very poor in OS/400.  If you add records to a data queue and for any
reason, the
program that removes records from the data queue is not running, then the
data
queue will expand to contain the buildup of records.  However, contrary to
what
you might expect, the size of the data queue never goes back down once the
records are removed.  At that point, you're stuck with a rather large data
queue
space and, as far as I've been able to see, the only recovery is to delete
the
data queue and then rebuild it from scratch.

Rich Loeber
Kisco Information Systems
http://www.kisco.com
  ------------------------------------------------------------------------

Don Tully Sr wrote:

There is absolutely no down side to reuse deleted records.  The

performance

issues are very close to zero.  All applications that I have written for

the

past 13 years have all files set to reuse deleted records.  It certainly
eliminates the downtime problems associated with file reorgs.

If you must guarantee that records are processed in write sequence, then

you

must add a key, perhaps timestamp.  Obviously the relative record number
will no longer indicate the sequence the records were written to the 

file.

If you want to go to the effort of using a data queue, that certainly

could

also be a way to go.  I have also written many data queue routines for

high

performance requirements.

Don Tully
Tully Consulting LLC

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of James H H Lampert
Sent: Monday, September 25, 2006 5:24 PM
To: midrange-l@xxxxxxxxxxxx
Subject: File that has records constantly being added and deleted

Here's the situation:

We have a file. Any arbitrary number of jobs can put
records into the file; a single dedicated job reads the
records, in arrival sequence, processes them, and deletes
them. We thus have a file that rarely has more than a few
active records, but accumulates lots and lots of deleted
ones.

Is there a way to squeeze out deleted records without
having to grab an exclusive lock on the file? Or would it
be more sensible to set it to re-use deleted records, and
modify the processing program to read by key? Or are there
other ideas?

--
JHHL
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