Hi Zoltan!
There is a formula to check your 'fragmentation' level to verify Remco's
explanation:

SELECT CAST((100 - (CAST(MAX_REDUCTION_MB AS FLOAT) * 256 ) /
(CAST(USABLE_PAGES AS FLOAT) - CAST(USED_PAGES AS FLOAT) ) * 100) AS
DECIMAL(4,2)) AS PERCENT_FRAG FROM DB

Kindest regards,
Eric van Loon
KLM Royal Dutch Airlines

-----Original Message-----
From: Remco Post [mailto:r.post AT SARA DOT NL]
Sent: Tuesday, July 22, 2003 16:42
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: Database numbers don't add up


On Tue, 22 Jul 2003 10:27:04 -0400
Zoltan Forray/AC/VCU <zforray AT VCU DOT EDU> wrote:

> TSM server V5.1.6.2 on z/OS.
>
> Can someone explain why these numbers from a Q DB F=D don't "add up" (at
> least they don't make sense to me ?):
>
>           Available Space (MB): 35,160
>         Assigned Capacity (MB): 35,160
>         Maximum Extension (MB): 0
>         Maximum Reduction (MB): 5,372
>              Page Size (bytes): 4,096
>             Total Usable Pages: 9,000,960
>                     Used Pages: 4,968,239
>                       Pct Util: 55.2
>                  Max. Pct Util: 55.2
>               Physical Volumes: 15
>
> In summary, it says that of the roughly 35GB DB, only 55% is used.  In
> round numbers, 20GB is in use. This means that 15GB is not.
>
> However, the "Maximum Reduction" value is 5GB.
>
> Where is the other 10GB ?
>


'In between', some people refer tot this as database fragmentation. There
are appereantly in your case, a lot op pages unused, but that cannot be
freed for database reduction. This probably has something to do with how TSM
allocates a fresh db page when it needs one, I'm guessing that it tries to
allocate pages in a way that leaves you with a as good as possible
performance. As long as you don't really need the diskspace, I wouldn't
worry. If you really do need the disks, I guess unloading than loading the
db will temporarely resolve this problem (and in the end will leavy you with
a db that performs far less than currently).

> Even if TSM kept the "reduction" values based on the volume sizes (roughly
> 2.3GB per 3390-3 volume is what it is reporting), I should still be able
> to reduce the size by 6-volumes, or roughly 13GB !


--
Met vriendelijke groeten,

Remco Post

SARA - Stichting Academisch Rekencentrum Amsterdam    http://www.sara.nl
High Performance Computing  Tel. +31 20 592 8008    Fax. +31 20 668 3167

"I really didn't foresee the Internet. But then, neither did the computer
industry. Not that that tells us very much of course - the computer industry
didn't even foresee that the century was going to end." -- Douglas Adams


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