RE: RPG Blocked Writes

In this particular case, the physical is keyed, as are some logicals, although none of them are Unique keys.

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Dennis Lovelady
Sent: Monday, June 07, 2010 5:50 PM
To: 'RPG programming on the IBM i / System i'
Subject: RE: RPG Blocked Writes

Not keying the physical won't help, if you have unique keys elsewhere. The
result is a constraint on the file that must be checked with each write -
and that means a physical write with each logical write.

I personally feel it's best to put your unique keys on the physical, but
again that won't impact the performance you're measuring.

Dennis Lovelady
http://www.linkedin.com/in/dennislovelady
--
"Abstract Art: A product of the untalented, sold by the unprincipled to the
utterly bewildered."
-- Al Capp

Aha, so it sounds like there is a reason to not key a physical? I
thought that the "sequential" and "keyed" access to a file as mentioned
by the document was in regard to what opcodes I was using, not the
actual access path. Bummer. However, good to know. A while back I
had asked if there was any reason to not key a PF, and I don't recall
that being an issue, however I may have also missed it.

Thanks,
Kurt

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-
bounces@xxxxxxxxxxxx] On Behalf Of Alan Campin
Sent: Monday, June 07, 2010 5:30 PM
To: RPG programming on the IBM i / System i
Subject: Re: RPG Blocked Writes

Are there unique keys on the table? That will change it to single
record
I/O.

On Mon, Jun 7, 2010 at 4:22 PM, Kurt Anderson
<kurt.anderson@xxxxxxxxxxxxxx>wrote:

I have a file defined in a program as:

FFileA O A E K Disk

From my understanding, writes to this file should be blocked.

However

when I look at the I/O for the job, the I/O count and the RRN is

always

equal. For comparison, reading a file that's blocked has a lower I/O

count

than the current RRN.

Is this a matter of me not understanding the I/O screen (when looking

at

the job as it is running), or is this file actually writing a single

record

at a time?

According to this document, I feel that these writes should be

blocked.

https://www-

912.ibm.com/s_dir/slkbase.NSF/1ac66549a21402188625680b0002037e/d6738e1c
d37e1f33862565c2007cef79?OpenDocument

"All high-level language programs (HLLs) use blocking at certain

times and

use single record I/O at other times, based on program

specifications.

Because blocking takes less system resources to perform a single I/O,

a

program that blocks performs better and uses less system resources.

The

default for the HLL uses record blocking if opening a file for output

only

(write) or input only (read)."

Thanks,
Kurt Anderson
Sr. Programmer/Analyst
CustomCall Data Systems