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CHGPF is ALWAYS faster than CPYF ... because it uses the Db2i engine "under the covers" so it performs much of the work below the MI layer.   It actually invokes the same logic as using an SQL ALTER TABLE to do the same thing.
By the way, you can actually use SQL ALTER TABLE ... directly, even against a *FILE PF that was originally created using DDS.


On Friday, January 22, 2021, 1:42:47 PM EST, smith5646midrange@xxxxxxxxx <smith5646midrange@xxxxxxxxx> wrote:

CHGPF never entered my mind even though I do use it occasionally.

For the files being converted with CPYF, we are doing a *MAP *DROP.
Anything that could not be handled via *MAP *DROP (i.e. an alpha field
changing from 2A to 3A and needing a leading zero added) are being converted
via a custom program.

Do you know that CHGPF is quicker than CPYF?  I supposed that might depend
on how many fields are changing.


-----Original Message-----
From: MIDRANGE-L <midrange-l-bounces@xxxxxxxxxxxxxxxxxx> On Behalf Of Rob
Berendt
Sent: Friday, January 22, 2021 1:17 PM
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxxxxxxxx>
Subject: RE: Converting large amount of data

Good point.  There are a number of people who never knew that many years ago
IBM allowed you to do the following to modify and add columns. 
CHGPF FILE(MYFILE) SRCFILE(MYLIB/QDDSSRC) They only remember the early
releases required you to copy from one file to another to modify/add
columns.

Rob Berendt
--
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to:  7310 Innovation Blvd, Suite 104
          Ft. Wayne, IN 46818
Ship to:  7310 Innovation Blvd, Dock 9C
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http://www.dekko.com


-----Original Message-----
From: MIDRANGE-L <midrange-l-bounces@xxxxxxxxxxxxxxxxxx> On Behalf Of x y
Sent: Friday, January 22, 2021 1:06 PM
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxxxxxxxx>
Subject: Re: Converting large amount of data

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Copy data into PF's without logicals, SQL indexes, or constraints
(referential integrity and such).

In CPYF, use FROMRCD(1) and COMPRESS(*NO) to try to force the system to do
a block copy.  You mentioned "new format", so you'll probably use
FMTOPT(*MAP *DROP); don't use it unless you need to.

WRT "new format", remember you can change your DDS source (multiple columns
at once) and then execute CHGPF (including the DDS source file and member
names) and the system will change the format for you; it's the equivalent
of SQL's ALTER TABLE.  *My experience suggests the logicals are magically
maintained through this process; this can be a major time-saving benefit*.
So, if you need to add new columns, resize others, change the text, edit
codes, or column headings, CHGPF is the way to go.  I've been midranging
since the days of the System/3 and using CHGPF to change the layout of a
file is IMO one of the top five enhancements ever.

On Fri, Jan 22, 2021 at 8:27 AM <smith5646midrange@xxxxxxxxx> wrote:

We have some files that are pretty big that we are going to be converting
to
a new format and I'm looking for some info on converting the data.



I am not looking for answers about splitting in threads or anything like
that.  We are converting over 700 files so threads will not help me.
Threads will just delay other files from being converted.



That said, I have one specific question that I am looking for an answer
on.



Is it more efficient to

1.      Create the new physical files and their logical files, and then
convert the data

or

2.      Create the new physical files, convert the data, and then add the
logical files



I know the machine has 3 CPUs with the ability to pull 3 more from the
pool.

I forget the memory but it is a pretty decent amount

There are 12 I/O channels.



If there is something else you need to know to give me an answer, please
ask.

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