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February 2004, Week 1

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Subject:
Re: 997 and memory
From:
Craig Lalley <[log in to unmask]>
Reply To:
Craig Lalley <[log in to unmask]>
Date:
Tue, 3 Feb 2004 06:55:05 -0800
Content-Type:
text/plain
Parts/Attachments:
text/plain (95 lines) 
Denys,

During the checkpoint the XM will scan memory for dirty pages to post.  This is
the notorious pin 11 or 12 that people see periodically on the system (pin 17
for N-class boxes).

Scanning memory creates a lot of system overhead and there is a patch to reduce
the effect of semaphore locking (MPEMX34A probably superseeded).

The real problem is when the second Checkpoint hits, before the first has time
to finish, i.e. they collide.  To compensate for this, it is possible to
increase the size of the XM logfile and reduce the time between checkpoints.

The good news is that the XM checkpoint is a serially threaded process, hence
it will only use up one processor (better have a few if you have 16GB of
memory).

The problems I am discussing are for very heavy, data entry systems.  The XM
(transaction manager) is a write cache.

Generally more memory will help batch reporting, it does not always help
on-line response times.

Hope that makes sense, it took me awhile to understand it.

-Craig


--- Denys Beauchemin <[log in to unmask]> wrote:
> Ok, explain how that would be painful.
>
> Denys
>
> -----Original Message-----
> From: HP-3000 Systems Discussion [mailto:[log in to unmask]]On
> Behalf Of Craig Lalley
> Sent: Tuesday, February 03, 2004 8:28 AM
> To: [log in to unmask]
> Subject: Re: [HP3000-L] 997 and memory
>
> Chuck, Dane, Joe and all,
>
> I humbly beg to differ, a 997 supports 16 GB of memory with standard HP
> memory.
>
> Although I do not recommend it.  The problem is the 180Mhz 997
> processor.  At
> 180 Mhz, it takes about 80 seconds to scan 16GB of memory.  That could
> make the
> XM checkpoints quite painful.
>
> -Craig
>
>
> --- Chuck Ciesinski <[log in to unmask]> wrote:
> > Dane, Joe, and all,
> >
> > I humbly beg to differ with Joe,  with third party arrays, you can get
> 16
> > GB in a 997.
> >
> >
> > Chuck Ciesinski
> > Hughes Network Systems
> > 11717 Exploration Lane
> > Germantown, MD  20876
> > p  301 601 2608
> > f   301 601 6303
> > email  [log in to unmask]
> > "The joy of life is living it..."  unknown
> >
> > * To join/leave the list, search archives, change list settings, *
> > * etc., please visit http://raven.utc.edu/archives/hp3000-l.html *
>
>
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