Re: REUSEDLT and performance

["Al Barsa, Jr." <barsa2@xxxxxxx>]

At 10:48 AM 2/1/01 -0600, you wrote:
>I have done a lot of detailed work here.  The only (significant)
>performance implications when using this feature occur if you are
>constantly adding/deleting records over the limit of the maximum number of 
>records in the file, which (IMHO) is not typical.
>----------
>
>Thanks for the concise answer, Al.  My only question is the meaning of the 
>above statement.  "over the limit of the maximum number of records in the 
>file" means to me that you are adding records past the total size of the 
>file (initial size + increment size * number of increments).  It was my 
>understanding that this will generate a system operator message, but your 
>message implies that you can get around this.  Are you talking about a 
>reply list entry, or some other means?


Joe,

I didn't explain this properly.  It has nothing to do with the system limit 
of the file.

When you have a file with "N" records, and then delete some.  Another job 
opens the file, and get's a "deleted record map" of the records that are 
deleted (at file open time).  As the file fills with records, there is a 
minimal performance hit when the file becomes full of records, and now 
needs to add records to the end of the file.  The other performance hit 
(also nominal) occurs when you are attempting to write a record to a 
deleted space (as determined from the "deleted record map" which was 
created at file open time), and find a spot that has already been written 
to by another job.  In the event that you opened a file with a million 
deleted records, and then they have all been written by another job, your 
write could be significantly impacted.

Joe, if you have any further questions, please call.




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Al Barsa, Jr. - Account for Midrange-L
Barsa Consulting Group, LLC.    
400 > 390

Phone:          914-251-1234
Fax:            914-251-9406
http://www.barsaconsulting.com
http://www.taatool.com

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