If you run journaling you can get a quick checkpoint. I did several tests
on our previous system (Model 520 Power 5+ running V5R3M5), and when I
issued a SAVLIB of our production data libraries in the middle of the
afternoon, using Save While Active, the system reported it reached a
checkpoint in less than 1 minute. This is while users were active, and the
system didn't slow down.
We're running a HA product, so that's journaling our files already, but it
may be worthwhile to implement journaling of your data libraries if
getting a quick SWA checkpoint is important.
Steve
- -
Steven Morrison
Fidelity Express
Charles Wilt <charles.wilt@xxxxxxxxx>
Sent by: midrange-l-bounces@xxxxxxxxxxxx
04/20/2009 03:31 PM
Please respond to
Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>
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Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>
cc
Subject
Re: Save While Active Question
Questions like this are when we really miss Al Barsa....
Here's my take:
Save While Active (SWA) offers 3 options
1) Hard
2) Easy
3) Ragged
Option 1) Hard provides for 100% uptime, but requires the use of
journallying and commitment control and the backup/recovery is so
difficult nobody uses it. A HA system is easier.
Option 2) Easy involves shutting down, or quiescing, the system
bringing it back up after the checkpoint has been reached.
Option 3) Ragged, which was added at v5r3, provides for faster
checkpointing than option 2, but requires journalling and commitment
control and involves a more complicated recovery than option 2.
One thing to keep in mind, with option 2 & 3 you can reduce the time
it takes to reach a checkpoint by reducing the # of objects that need
to be checkpointed. For example, if you save 10 libraries, but only
one has objects in use, do a SWA on the one and a regular save on the
others. Ideally, you'd move all the active objects to a single
library. In you're case, those 10-12 files you mention would ideally
be in a library by themselves.
Lastly, while both the easy and the ragged recommend quiescing the
system, you can do SWA without shutting down the application as long
as there's an opportunity for the system to do the checkpoint. For
example, lets say the only activity is a batch process that runs
continually in a loop with a DLYJOB before restarting. The DLYJOB
might be enough time for the checkpointing to occur. Or for example,
you've only got a few users on the system, it's likely the system can
get the checkpointing done during the users "think time".
When you have lots or users, or lots of processes that you can't
control, then quiescing the system is often the only way to go.
HTH,
Charles
On Mon, Apr 20, 2009 at 8:16 AM, John Candidi
<jacandidi@xxxxxxxxxxxxxxxxx> wrote:
John A. Candidi
American European Insurance Group
AS400 & POINT Application Manager
856-779-2274
jacandidi@xxxxxxxxxxxxxxxxx<mailto:jacandidi@xxxxxxxxxxxxxxxxx>
-----Original Message-----
From: John Candidi
Sent: Monday, April 20, 2009 8:01 AM
To: 'midrange-l-owner@xxxxxxxxxxxx'
Subject: Save While Active Question
We have about 20 libraries we save every night to a 3580 tape drive. 2
of them have quite a few objects. We are being asked to allow some form of
processing each night while the save is going on so I wanted to use the
save while active option? Currently, the backup takes only about 45
minutes. In anybody's experience, will this increase the time it takes to
run the backup or cause any other problems in your experience? It really
all boils down to the potential that 10-12 files may open from ONE of the
libraries at some point during the save. The system is not in a restricted
state while doing this save since they are all basically user libraries.
John A. Candidi
American European Insurance Group
AS400 & POINT Application Manager
856-779-2274
jacandidi@xxxxxxxxxxxxxxxxx<mailto:jacandidi@xxxxxxxxxxxxxxxxx>
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