× The internal search function is temporarily non-functional. The current search engine is no longer viable and we are researching alternatives.
As a stop gap measure, we are using Google's custom search engine service.
If you know of an easy to use, open source, search engine ... please contact support@midrange.com.


  • Subject: Re: DS fields
  • From: dhandy@xxxxxxxxxxx (Douglas Handy)
  • Date: Tue, 13 Jul 1999 17:30:40 GMT

Dave,

Doug said:

>>  Subfields are not pointers per se, they just have addresses within the
>> address space for the DS as a whole.

Dave said:

>If that is the case, then how do you account for a field from a file that
>is "sub divided" in a DS?

(snip) 

>In this case, a portion of the DS is altered, and the updated Acct# is
>written to MasterFile.  I thought that the Acct# DS had a pointer to
>the I/O buffer where MasterFile is read from & written from.
>If pointers aren't used, how does this the change in the DS show
>up in the change in the file?

All fields are stored in memory separate from the I/O buffer.  The
fields are not pointers to within the buffer space.  After a record is
read, each field is moved from the buffer to the field's memory space.

The opposite happens when a record is written.  First the fields are
moved to the buffer, then the buffer is written.

If you have ever run a program in debug and tried to step into a disk
I/O operation, that is why you need to step over each field's movement
to/from the buffer.  This can by suppressed in RPG IV by using the
H-spec keyword Option( *NoDebugIO ), but is the default behavior.

So if you have a DB field as part of a DS, then overlay a portion of
the field, the DB field is copied to the buffer prior to the write and
the disk record reflects the overlay.

Doug
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* This is the RPG/400 Discussion Mailing List!  To submit a new         *
* message, send your mail to "RPG400-L@midrange.com".  To unsubscribe   *
* from this list send email to MAJORDOMO@midrange.com and specify       *
* 'unsubscribe RPG400-L' in the body of your message.  Questions should *
* be directed to the list owner / operator: david@midrange.com          *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *


As an Amazon Associate we earn from qualifying purchases.

This thread ...

Replies:

Follow On AppleNews
Return to Archive home page | Return to MIDRANGE.COM home page

This mailing list archive is Copyright 1997-2024 by midrange.com and David Gibbs as a compilation work. Use of the archive is restricted to research of a business or technical nature. Any other uses are prohibited. Full details are available on our policy page. If you have questions about this, please contact [javascript protected email address].

Operating expenses for this site are earned using the Amazon Associate program and Google Adsense.