On our test installation (TSM 4.1.4.1, AIX 4.3.3ML6) we've seen a strange
behavior:
1. Client backups to disk pool
2. Migration starts after HIGHMIG limit is passed
3. Client fills the pool faster than migration frees it
4. Reaching disk pool 100% full client pauses indicating "waiting for mount
of offline media"
5. Migration process commits a migration transaction freeing space in disk
pool. Client does NOT resume.
6. Migration process finishes (it's a loooong process). Client wakes up and
continues backup.
7. Administrator reduces disk pool deleting some volumes (to produce more
pool fills)
8. Client fills the pool again and blocks
9. Migration finishes. Client again resumes.
8. ...
9. ...
8. ...
9. ... (many times)
I do not know is this a bug in the release we are using or a feature of all
releases but test this on your platform. If you lower significantly LOWMIG
threshold and something like this happens you can see long waits and backup
can go out the backup window.

Zlatko Krastev
IT Consultant





Alan Davenport <Alan.Davenport AT SELECTIVE DOT COM> on 26.10.2001 18:03:38
Please respond to "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
To:     ADSM-L AT VM.MARIST DOT EDU
cc:

Subject:        Re: Spill processing please help

+ -----Original Message-----
+ From: Doherty, John (ANFIS) [mailto:john.doherty AT ANFIS.CO DOT UK]
+ Sent: Friday, October 26, 2001 10:21 AM
+ To: ADSM-L AT VM.MARIST DOT EDU
+ Subject: Re: Spill processing please help
+
+
+ Thanks Alan, this looks good.  This is very similar to the
+ problem we have.
+ For example I run migration on our 3 disk pools to clear them
+ down at 18:00,
+ 21:00 and 22:00 respectively.  they finish at 18:32, 21:30 and 22:30
+ respectively.  Can I assume any migration after 22:30 would
+ indicate spill
+ processing is occurring ??

Yes, that is exactly what I was trying to say. Any migration that you
didn't
trigger yourself is due to your pool hitting the HIGHMIGPCT limit.

If your pool is filling up too often here is a little trick you may want to
try. Set your LOW migration threshold to 10% or so but leave your high
migration threshold at 90%. If tape contention with other users is not an
issue this will nearly empty the pool if any unscheduled migration is to
occur. (Setting low migration to ZERO during the backup window is not
recommended because as SOON as a file hits the disc pool it will migrate
causing lots of tape mounts!)
+
+ Also I may utilize the 1 GB file limit, but I assume that
+ every time a file
+ is greater than 1 GB then a tape mount would be requested ???

Yes, it will. But if you are using collocation like I am the amount of tape
mounts will be much less for the over sized files than if triggered
migration were to occur. Setting a max file size on the disc pool is one
way
of reducing the frequency of triggered migration.

In a perfect world our disc pools would be large enough to hold everything
from a backup window but we all know that's not always possible. I'm afraid
the DASD Czar would come after me with sharp objects if I were to try to
get
any more packs this month. (:

 Take care,
     Al

Alan Davenport
Senior Storage Administrator
Selective Insurance
alan.davenport AT selective DOT com
(973)948-1306