Re: RGZPFM -- MIDRANGE-L

In the system/3 you could build a master and a data file with the samerecord length and place them in the fixed disk and removable disk insuch a way that both files where read with the head in the same postion.

Since we have moved to the system/34 IBM people have tryed to convinceme to leave it up to the computer to place the files, and when wereached the AS/400, (in '89), I finally realized it is the best idea.

RGZPFM will recover space, and in some cases will improve speed, but ingeneral it will not be significant.

The data that is used more often must go in the center of the disk, notin the borders. In practice realy it will be in main memmory or in thecontroler's buffer, so the physical location will not be so relevant.

___________________________________________________________________________________________
Ryan Hunt wrote:

A couple people have refered to proper data balance across striped volumes
as synomous with contigous clusters/sectors on an individual disk (or at
least that's how I read it).

My disks are perfectly balanced (or at least I desire no better
balancing)...that's not what I was going for.  Someone also stated that HD
heads will be all over the place so there would be no advantage to
contiguous disk usage.  I disagree with this.

Having data spread contiguously on disk will promote sequential file reads
instead of many non-sequential reads with latency lags for the same
non-contiguous file.  Sure, there will be interrupts to service many user
requests, but wouldn't interrupts + non sequential file reads exacerbate the
issue?

I once had an IBM tech suggest using the CPYLIB / RSTLIB to re-spread large
libraries across disks because RSTLIB will rebuild each file one at a time
and keep data contiguous at the disk level.  In fact, if you really wanted
to put the time in, you could copy files/tables one-by-one with your largest
(or most likely to be scanned) tables first so the are both contiguous and
as close to the outer edges of the disks as possible.

Anyway, obviously RGZPFM is not going to do want I needed.  Thanks for all
the responses.

Ryan

"Luis Rodriguez" <luisrodriguez@xxxxxxxxxxx>
wrote in message
news:1143752622.10391.257948192@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Ryan,

1) RGZPFM reorganizes only 1 member at a time. The default is *FIRST.

2) Usually, in the AS/400, you don't define a file as having contiguous
sectors on your disk. In fact, as your system has several disks, it
balances them automatically so you get better performance that way.

Regards,

Luis Rodriguez

------------------------------

message: 8
date: Thu, 30 Mar 2006 15:21:01 -0500
from: "Ryan Hunt" <ryan.hunt@xxxxxxxxxxxxx>
subject: RGZPFM

We've had our AS400 for 6 years now and we've never performed an RGZPFM
on
our production database. Our AS400 serves as our Enterprise Server for a
JDE
OneWorld ERP so there is LOTS of activity on this thing.

I'm under the impression that the running RGZPFM again my production DB
library with no other parameters will remove deleted records from all
members and place the members/files into contiguous sectors of my disks
(thus making sequential I/O more likely).  Is this correct?

Thanks in advance.

Ryan Hunt

----------------------------
Luis Rodriguez
IBM Certified Systems Expert
eServer i5 iSeries Technical Solutions
Caracas, Venezuela