RE: Rif: Re: Help!!!!! Access path size

["Richard Jackson" <richardjackson@xxxxxxxxxxxxxxxxxx>]

Depending on your setting for QQRYDEGREE, you might have been building
access paths using one CPU.  Depending on the size of the memory pool that
you were in and the number of activity levels, you might have had been
rebuilding paths in a very small memory space.  If your disk drives were
protected with mirroring, the cost to write new index pages may have been
small.  If protected with RAID and you used parallel index build, you could
generate a high level of disk contention.

On the other hand, if many of your access paths were shared, you might have
actually rebuilt very few real indexes.

If it works, it is okay.  If it worked before then it suddenly doesn't work
and you don't know why, you might find yourself in a world of hurt.  If you
know how it works, you can make it go as fast as possible.

Richard Jackson
mailto:richardjackson@richardjackson.net
http://www.richardjacksonltd.com
Voice: 1 (303) 808-8058
Fax:   1 (303) 663-4325

-----Original Message-----
From: owner-midrange-l@midrange.com
[mailto:owner-midrange-l@midrange.com]On Behalf Of dkeck@idt.net
Sent: Friday, August 25, 2000 5:30 AM
To: MIDRANGE-L@midrange.com
Subject: Re: Rif: Re: Help!!!!! Access path size


I don't see the reason for your approach (too much work).  When I decided to
upgrade our LF's to ACCPTHSIZ *MAX1TB, I created a PDM user option to do
just
that with the CHGLF command, and ugraded them in groups, by name, over 3
weekends.  There were thousands of access paths, with quite a few referring
to
tens of millions of records.  For the vast majority of them there was no
rebuild of the access path (ie. instant conversion), irrespective of the
size
of the access path.  This was done on a 12-way box with 96 gig main storage
within 1 interactive job (ie. using only one of the processors).  -DaveK

> I would add 3 steps:
>
> 1A) Change all logicals to be access path maintenance
> *DLY
> 2A) Change back the logicals to *IMMED
> 2B) Open the logicals with a pgm and let them rebuild
> the acces path.
>
> This looks to me to be a little bit faster. We
> experienced a copy of a 25Gb indexed PF to an empty
> one with 4 LF attached to it, without making those
> logicals to be *DLY and it really was a bloody bath.
>
> Simone Pacciarini
> _____________________________________________________
> The fastest possible way to convert the access paths
> (from the time you
> start until all are done) is to do the following:
>
> 1) Create a blank set of physical/logical files with
> the attributes you want.
>
> 2) Create an RPG program or REXX script to read from
> the old file into
> the new file and run it.  CPYF will not produce the
> results you want, as
> it invalidates and rebuilds the logicals
>
> 3) Replace the old files with the new files.
>
> This is the fastest beginning to end because all the
> indexes are updated
> as records are added to the file.  Any other method
> will read all the
> records in the physical file up to 50 times.  It may
> be less due to
> access path sharing, but it isn't likely to be much
> less.
>
>
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