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:[EMAIL PROTECTED]
Sent: Tuesday, July 22, 2003 16:42
To: [EMAIL PROTECTED]
Subject: Re: Database numbers don't add up
On Tue, 22 Jul 2003 10:27:04 -0400
Zoltan Forray/AC/VCU [EMAIL PROTECTED] 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 Amsterdamhttp://www.sara.nl
High Performance Computing Tel. +31 20 592 8008Fax. +31 20 668 3167
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