1. Never make it larger than 12GB! Someday, your log will fill up, and
you've got to have room under the 13gb limit to be able to add an
emergency extent, otherwise you'll find yourself dug in so deep you
can't dig out.

2. You will find it a convenience to make it two 6gb halves. That way
you can move it around with the server up. Also you can move from your
present configuration with the server up - trim down to six 1gb pieces,
add your first new 6gb chunk, delete the six old 1gb pieces, and now add
the second 6gb extent. All without ever bringing the server down.

It is OK to put the two 6gb extents on the same physical volume. (Best
if adjacent to one another.) The log is write-mostly, and it is written
sequentially. It will fill up one half and then start writing the
second. Therefore there is no penalty to splitting it even on the save
PV, and also there is little advantage to splitting it across two
different PVs. The log has a COMPLETELY different I/O model than the
database.

Roger Deschner      University of Illinois at Chicago     rogerd AT uic DOT edu
"Have you ever, like, tried to put together a bicycle in public? Or a
grill?" Astronauts David Wolf and Piers Sellers, explaining the
difficulties encountered in attaching equipment to the Space Station


On Thu, 25 Mar 2004, Thach, Kevin G wrote:

>It's not a requirement, I am just acting on IBM's recommendation to put
>the log on a single volume for performance reasons.  2 would still be
>better than the 8 I have now.
>
>Thanks!
>
>-----Original Message-----
>From: Prather, Wanda [mailto:Wanda.Prather AT JHUAPL DOT EDU]
>Sent: Thursday, March 25, 2004 3:01 PM
>To: ADSM-L AT VM.MARIST DOT EDU
>Subject: Re: Question about recovery log
>
>
>I believe you are correct.
>But why do you have a requirement to have only 1 log file?
>The log is written sequentially, so I don't see that it would hurt you
>to have two 6.5 GB logs, instead of one 13GB log...
>
>-----Original Message-----
>From: Thach, Kevin G [mailto:KThach AT COVHLTH DOT COM]
>Sent: Thursday, March 25, 2004 2:57 PM
>To: ADSM-L AT VM.MARIST DOT EDU
>Subject: Re: Question about recovery log
>
>
>That's what I do with my DB, but by defining the new log volume and
>adding it, I will be over the 13GB limit until I've removed all the old
>volumes.  Will TSM let me do that?  I guess I could try it and see.
>
>-----Original Message-----
>From: Davidson, Becky [mailto:Becky.Davidson AT SLBG DOT COM]
>Sent: Thursday, March 25, 2004 2:50 PM
>To: ADSM-L AT VM.MARIST DOT EDU
>Subject: Re: Question about recovery log
>
>
>Define the new and add it and then delete the old. Don't forget to
>mirror.
>
>-----Original Message-----
>From: Thach, Kevin G [mailto:KThach AT COVHLTH DOT COM]
>Sent: Thursday, March 25, 2004 1:42 PM
>To: ADSM-L AT VM.MARIST DOT EDU
>Subject: Question about recovery log
>
>
>I'm confused about how I should go about changing the configuration of
>my recovery log.  I'm hoping someone can point me in the right
>direction.
>
>I currently have eight, 1GB log volumes, and I'm wanting to replace
>these with a single 13GB volume.
>
>Normally, I would just create and define the new volume using the def
>dbvol command, and then remove the old volumes, but since there is a
>13GB limit on the recovery log, I can't do that.
>
>What's the best way for me to do this?  Is there any way I can do it
>with the server up and running?  Switch to Normal mode, remove the old
>volumes, create the new one, etc.  I'm assuming that TSM will not allow
>me to completely get rid of all my log volumes while the server is up
>(even if in Normal mode), which is what I would have to do in order to
>add the 13GB one.
>
>
>Do I need to shut down the server, remove the old volumes and define the
>new one with the dsmfmt -m -log command?
>
>I'm running TSM 5.1.7.3 on AIX 5.1
>
>Thanks!
>