Re: Using VARLEN DDS keyword

["R. Bruce Hoffman, Jr." <rbruceh@xxxxxxxxxxxxx>]

Yes, there is overhead for variable length storage. I don't recall exactly,
but I seem to have the number 13 in my head.

Variable length fields are stored in the source table as a fixed length
field plus the overhead bytes. The variable portion is in another area,
outside the source table. The 13 bytes links them.

So, given your example, and my assumed 13....

orginal file 25
varlen file 4+13=17 plus overflow area that contains the variable
portion....

So you see, you might not actually save space.

My personal rule of thumb is 20%. If 80% of the file is 10 characters but
some must be 50 characters, then I would lean toward using varlen.  But most
often it's more like some must be 256 while 95% of the file is under 30
characters.


===========================================================
R. Bruce Hoffman, Jr.
 -- IBM Certified Specialist - AS/400 Administrator
 -- IBM Certified Specialist - RPG IV Developer

"Those who would give up essential Liberty,
  to purchase a little temporary Safety,
  deserve neither Liberty nor Safety."

     - The Papers of Ben Franklin

-----Original Message-----
From: Neil Goldenberg <Goldenbergn@technocrats.co.uk>
To: 'RPG400-L@midrange.com' <RPG400-L@midrange.com>
Date: Monday, January 15, 2001 8:16 AM
Subject: Using VARLEN DDS keyword


>Hi,
>
>I have been trying to use VARLEN to reduce the size of some files (with
>and without variable length keyed fields), but when I make comparisons
>between identical files (each containing the same number of records)
>except for one having variable length fields, and the other not, using
>DSPFD and checking  'Data space size in bytes' or 'Total of member
>sizes' the file using variable length fields is not always smaller,
>indeed it can be slightly bigger.
>I have made comparisons with different number of records in the files.
>
>I have coded the variable length field as follows:-
>
> FIELDA          25            VARLEN(4)
>
>Any comments?
>
>Regards
>Neil
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