Re: Justa note of thanks

Hi Nelson,

I think(?) Barbara was referring to Varying fields in RPG as opposed to Varying 
fields defined in a database.

The use of varying fields in a database are still a large "depends". There is 
an overhead with any field whose contents exceed the constant portion defined 
for every record. The extra characters are stored in
an overflow area. Therefore, reading a record would probably require two pages 
being input to memory.

e.g.
                        NAME                     30                            
VARLEN(5)

If NAME has a value of "Paul Tuohy", then "Paul " is stored in the record and 
"Tuohy" is stored in the overflow. Both the record and the overflow must be 
accessed to get the complete field.

There is also an additional overhead in that the DBM must maintain a pointer 
from the record to the overflow area.

HTH

Paul Tuohy

"Smith, Nelson" wrote:

> Excellent article Jon (I have a large collection of Jon & Susan tomes), but
> I was inquiring more about Barbara's comment about routinely using the
> Varying keyword.
>
> I notice in many (or most?) PC languages they seem to routinely use VarChar
> types everywhere.  Do you think that is something we should do in RPG on all
> but the smallest of fields (flags, indicators, or code fields) on a more
> routine basis.  I think we have traditionally thought of using Varying only
> on big text descriptions fields, and such.  But there must be millions of
> files out there with 30 char name and address lines and that sort of thing.
> Making these variable length would have probably saved a few disk drives
> over the years.  Do you find yourself using Varying on more of these types
> of fields "just for the sake of it"?
>
> > -----Original Message-----
> > From: Jon Paris [SMTP:Jon.Paris@Partner400.com]
> > Sent: Friday, August 30, 2002 6:38 PM
> > To:   midrange-l@midrange.com
> > Subject:      Justa note of thanks
> >
> >  >> is that something we should begin doing routinely?
> >
> > If you check this wee article
> > (http://www.eservercomputing.com/iseries/articles/index.asp?id=146)
> > Nelson,
> > you'll see why I love VARYING fields.  There are many many uses for them,
> > but don't just use them for the sake of it - use them where they make
> > sense.
> >
> > Jon Paris
> > Partner400
> >