Re: What is the effect of deleted records on program performance?

It depends :)

A delete percentage of 20% is pretty high. Consider that data is
moved in blocks, so on average 20% of the data you're moving between
disk and memory is deleted. Now say you've got a report that reads
10% of the active records, you might do 2% less i/o if you didn't have
deleted records. Not too big a deal. On the other hand, if the
reports reads 100% of the records, you could do 20% less i/o if you
didn't have deleted records!

The above is pretty straight forward for sequence access, when doing
random i/o, it's less obvious but still a factor depending on the
amount of memory and thus cache available. If 20% of the records in
the cache are deleted, then you've wasted 20% of your cache space.

-Charles

On Thu, Sep 24, 2009 at 12:28 PM, sjl <sjl_abc@xxxxxxxxxxx> wrote:

Mark wrote:

 Did you mean, "What is the effect of "Reuse deleted records = *YES"?

 Or do you mean a physical file (with REUSEDLT=*NO)
 where new records are appended to the end of the file,
 and deleted records just marked as deleted,
 and create "holes", until you run a RGZPGM ...?


Mark -

The latter.

I am mainly interested in whether or not a program will perform better
against a file that has been reorganized to remove deleted records.

We have some programs which use SQL, but this is a JDE Shop using
DreamWriter, which dynamically builds and executes the OPNQRYF before
calling the RPG program.

For example, the file in question has 100,000,000 records with 20,000,000
deleted records.

- sjl


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