RE: File that has records constantly being added and deleted

With all due respect, there are some downsides.

First of all, you will be reading the file keyed, so that's more overhead.

Secondly, when you open the file, the job opening it sets up a "deleted
records map" (my term, not necessarily IBM's), to determine where it can
deposit deleted records, until it has to deposit them at the end of the
file.  Every job opening the file has to do this task, and different jobs
starting at different times will get different maps.

In the early days of REUSEDLT (when CPW was very low) we noticed a
performance hit when a job filled it's deleted records map, and started to
deposit records at the end of the file.  That hit may have been fixed, or
it may now longer be noticeable with faster systems.

Al

Al Barsa, Jr.
Barsa Consulting Group, LLC

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             "Don Tully Sr"                                                
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             AM                        RE: File that has records           
                                       constantly being added and deleted  
                                                                           
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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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