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

["Shaw, David" <dshaw@xxxxxxxxxxx>]

Bob,

Have you done benchmark comparisons on this?  It's been a long time (the
boxes were white, the first one was a /38), but I have a few times and I
always found it took less total time to rebuild the indexes after copying
the data, rather than leaving them to update record-by-record during the
copy.  Perhaps something's changed, or perhaps your system has some unusual
memory pool tuning or something.  

Hmm, I might be able to benchmark on our second 720 (the mirror that isn't
running yet), if I can make a little time to set it up.  If I get to it,
I'll post results.

Dave Shaw
Spartan International, Inc.
Spartanburg, SC

-----Original Message-----
From: Bob Buchanan [mailto:BobbyB@camstar.com]
Sent: Friday, August 25, 2000 5:58 PM
To: MIDRANGE-L@midrange.com
Subject: Re: Rif: Re: Help!!!!! Access path size


You do not want to have the system rebuild the access paths!  It has to
re-read the entire physical file, and you don't want that to happen.  It
takes longer to copy the file, but when you are done, you are done. 
Otherwise, you have to wait for the access paths to be rebuilt, and with
a large file, that takes quite a bit of time.  Especially on a smaller
system.
-Bob

> Simone Pacciarini wrote:
> 
> 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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