RE: Date field's and their file space usage.

Date fields are all stored internally as a 4-byte integer. The value stored
is the number of days since January 1, 0001 or October 14, 1582, I'm not
sure which it is.
When a database record is touched (retrieved for any reason) the internal
code converts the date from the internal form to what's called the External
Form. The external form is the only format you or I can see and the only
form RPG IV, C and other languages can see. 
Originally, if you read a DB record 1000 times, the date fields in that
record were converted from the internal form to the external form 1000
times. This was one of three reasons why, years ago, I opted to avoid date
data type fields in database. The other two where because IBM did not
support date fields in DDS display files or print files (which, since V4R2
has been corrected) and RPGIII continues to not support them.
We've pounded on the IBMers who owned the code for date data-types. I don't
know if they've fixed that performance issue or not, but for large databases
(those that exceed a few million records) I still avoid date data-types. But
for smaller databases, I'll always opt to use them.
-Bob Cozzi


-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx]
On Behalf Of rob@xxxxxxxxx
Sent: Tuesday, January 11, 2005 9:16 AM
To: RPG programming on the AS400 / iSeries
Subject: Re: Date field's and their file space usage.

Looks like 10 bytes to me.  But I am sure there is an explanation.

Rob Berendt
-- 
Group Dekko Services, LLC
Dept 01.073
PO Box 2000
Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





RPower@xxxxxxxxxx 
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Re: Date field's and their file space usage.






I thought actual date fields included the date separators?  Wouldn't that 
match what you have there?  Thus 5 bytes?

Ron Power
Programmer
Information Services
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P.O. Box 908
St. John's, NL
A1C 5M2
Tel: 709-576-8132
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rob@xxxxxxxxx 
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Date field's and their file space usage.






Barb,

We've been conditioned to believe that date fields only take up, what, 4 
bytes?  However when I do a DSPPFM on a date field I see:
*...+....1
2005-01-01
FFFF6FF6FF
2005001001

Has DSPPFM been customized just to make date fields look like they take up 


bytes?  Do they really take up this much space?  Or to see the real space 
only the use of DMPOBJ will work?


Rob Berendt
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Group Dekko Services, LLC
Dept 01.073
PO Box 2000
Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





Tony Carolla <carolla@xxxxxxxxx> 
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01/10/2005 05:41 PM
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Re: Varying Length fields, and LikeRec






Thanks!  That clears it up.  I guess I assumed that DSPPFM would show
the actual offsets within the record, based on the length of the
varying fields.  I am getting x'0034', or 52, which is the correct
length.

I am glad the VARLEN and VARYING keywords work like that. 


On Mon, 10 Jan 2005 17:27:54 -0500, Barbara Morris <bmorris@xxxxxxxxxx> 
wrote:
> Tony Carolla wrote:
> >
> > I am writing to a file, and one of the fields is a 150 Alpha VARLEN
> > field.  This file will contain a large number of history records, and
> > I am doing this to conserve space:
> > ...
> > In debug, I see that the DS has the correct length set (52) using %Len
> > to test the length.  But when I write, the field in the DB file
> > contains all 150 characters, with trailing spaces added.  Is there a
> > trick to making the WRITE op recognize the DS variable length, that
> > the compiler created for me, based on the file structure, or do I have
> > to eval %Trim from the DS to the actual file buffer fields?
> >
> 
> How are you determining the actual data in the file?  If you're using
> DSPPFM, the position of the other fields in the record will be fixed, so
> DSPPFM has to show something in those unused bytes.  Try doing F10 F11
> to see the hex value of the record, so you can see the 2-byte length
> part of the varying field.
> 
> For this file:
> A          R REC
> A            FLD1          10A
> A            FLD2          10A         VARLEN
> A            FLD3          10A
> 
> My record has values FLd1='aaaaaaaaaa', FLD2='bbb', and
> FLd3='cccccccccc'.
> 
> DSPPFM and it shows this:
>         aaaaaaaaaabbb       cccccccccc
> 
> With F10 then F11, it shows this.  The xx marks the 2 length bytes for
> FLD2 (value x'0003' = 3).
>                   xx
>         aaaaaaaaaabbb       cccccccccc
>         88888888880088844444448888888888
>         11111111110322200000003333333333
> 
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> 


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