Re: RGZPFM -- MIDRANGE-L

Ryan,

First, let me apologize as I believe that maybe my answer wasn't as clear orelevant as you needed. My native language is not English and sometimes Ihave some problem getting my ideas across.

When you create a file (CRTPF), OS/400 allows the data to be stored acrossseveral disks and, as better guys than me have explained in this forum, thisallows faster and better access to your info. That's the reason why,depending on your hardware and workload type, sometimes having few disk armscan represent a performance problem. Nowadays this can often be resolved, inpart, thru the use of IO adapters with a very big disk cache memory. Let merecommend the following document:


www.ibm.com/servers/eserver/iseries/perfmgmt/pdf/V5R2FiSArmct.pdf

That said, if you really want to have a file created with contiguoussectors, the CRTPF command has a parameter that allows you to do this:CONTIG (*NO/YES). As per the manual:


CONTIG

Specifies whether records in the initial allocation in each physical filemember are stored contiguously (next to each other) on auxiliary storage. Ifso, and the necessary contiguous space is unavailable, the system sends amessage to the job log and allocates the storage space noncontiguously. Thefile is still entirely usable. This parameter does not affect additionalallocations that might be needed later, which would probably benoncontiguous.

*NO: The storage space for each member does not have to be contiguous.

*YES: The system allocates contiguous space for each member of the physicalfile being added. If it cannot, the user is notified and a message is put inthe job log. The affected member is still added, even if the storage spaceis allocated noncontiguously. The member is just as usable in noncontiguousform. If *YES is specified for CONTIG, then ALLOCATE(*YES) must also bespecified.



Hope this helps.

Best Regards,

Luis Rodríguez

IBM Certified Systems Expert
eServer i5 iSeries Technical Solutions

Caracas, Venezuela

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

message: 3
date: Fri, 31 Mar 2006 14:13:43 -0500
from: "Ryan Hunt" <ryan.hunt@xxxxxxxxxxxxx>
subject: Re: RGZPFM

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 exacerbatethe

issue?

I once had an IBM tech suggest using the CPYLIB / RSTLIB to re-spreadlarge

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 yourlargest

(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