Re: ACCPTHSIZ perfomance - *MAX1TB vs *MAX4GB

[David & Eileen Keck <bstars@xxxxxxxxxxxxx>]

A couple years back the firm I was with was testing JDE OneWorld, which was
ODBC based.  Due to multi-minute response times, possible performance
adjustments were examined ... *MAX1TB was one of them.  After changing the
files related to the test (always all LF for a given PF) performance
improved dramatically, though response time never became acceptable.  After
reading up on ACCPTHSIZ I changed all files in the system on a Sunday using
a PDM user option (thousands of files, some over 100,000,000 records, about
70 Gig overall).  OS/400 uses a different algorithm to access records when
using MAX1TB vs *Max4GB.  That algorithm is usually but not always faster.
You asked about mixing *MAXxxx methods for LF's relating a common PF ... I
can't see any reason to do that.
-Dave K.

----- Original Message -----
From: <prumschlag@phdinc.com>
To: <midrange-l@midrange.com>
Sent: Thursday, January 03, 2002 2:54 PM
Subject: ACCPTHSIZ perfomance - *MAX1TB vs *MAX4GB


>
>
> I found this in the Archives, and I am looking for futher detail.  The IBM
> Redbook "AS/400 Availability and Recovery..." recommends all logicals
related to
> a physical should be 1TB or 4GB, but do not mix them.  It refers to
performance
> issues if you mix them, but it is not clear if they are referring to
overall
> performance, or performance in a specific program.  Anyone have any
success
> stories  with this?  I need to resolve a serious (2 minute) response time
issue.
>
> Phil
>
>
>
>    -----------------------------------------------------------------------
---------
>
>    Subject: Re: CISC to RISC and Excessive Logical I/O
>    From: "Mark Phippard" <MarkP@xxxxxxxxxxxxxxx>
>    Date: Wed, 20 Jun 2001 10:31:48 -0400
>
>    -----------------------------------------------------------------------
---------
>
>
>    Tom,
>
>    Do a DSPFD on the PF and all of its associated LF's and look at the
Access
>    Path Size (ACCPTHSIZ) parameter.  If the PF and LF's do not have the
same
>    value in this field, it can cause performance problems.  For best
>    performance, IBM recommends you change the value to *MAX1TB on all
files.
>
>    Maybe the PF came over with *MAX4GB and the LF's have been created on
the
>    RISC box with the new default of *MAX1TB?
>
>    Hope this helps.
>
>    Mark Phippard
>
>
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