Re: REUSEDLT and performance

Joe,

I have not done any experiments with this, but what I was told
by people I trust at COMMON meetings is that the performance impact
of searching for an available deleted record is small if there are
deleted records to find.  The worst case is when there is only one
deleted record, the result is a lot of searching.  If you have a
situation where you delete a lot of records at the beginning of the
day/week/month and then add records all day/week/month, the
performance impact will be small until the number of records
added approaches the number deleted.  After the "last" deleted
record is replaced, add-a-record will be a lot faster than right
before the "last" deleted record is found and reused.

If you have a large file and you delete one record and then add
one record all day long -- this feature could hurt...

If anyone has performance numbers from any tests I am very
interested in seeing them.

Charly
Geezer in Gig Harbor


>From: "Joe Pluta" <joepluta@plutabrothers.com>
>Reply-To: MIDRANGE-L@midrange.com
>To: <MIDRANGE-L@midrange.com>
>Subject: REUSEDLT and performance
>Date: Thu,  1 Feb 2001 09:07:35 -0600
>
>Are there performance implications when using REUSEDLT, especially on 
>really large files? I have to think that there is at least some performance 
>hit when REUSEDLT is enabled for files with millions of records. I'd guess 
>that the system keeps some sort of index of deleted records, and serves one 
>of those up when a WRITE is issued. I suppose, done correctly, the 
>performance implications aren't too great; it would only affect deletes 
>(add an entry to the index) and writes (fetch the record number from the 
>index rather than just use the next sequential record).
>
>Has anybody looked at this in any detail?
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