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Tablespace Size Calc : Right or Wrong

 
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sushanth bobby

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Joined: 29 Jul 2008
Posts: 1013
Location: India

PostPosted: Tue Sep 23, 2008 2:52 pm    Post subject: Tablespace Size Calc : Right or Wrong
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Hi,

I prepare a DB2 Extent report that looks like this...


Code:
DBNAME   TSNAME   PQTY-Allocated   PQTY-USED   SQTY-A   SQTY-U   E X T E N T S
        (TRKS)       (TRKS)   (TRKS)   (TRKS)                     TAKEN   REMAIN
dbname   tsname   2085             2085        3780     3619     27      8   


The table in this tablespace has 982,782 records and row length is 189.

Since primary(allocated & used) are in tracks. I calculated the size of the tablespace, taking following into condsideration.

16,384 cylinders/ disk
80 heads / cylinder
63 sectors / track
512 bytes / sector

I have calculated the following
Tracks = 2085

2085* 63 =131355 (Sector)
131355*512 =67253760 (bytes)
67253760/1024 =65677.5(kb)
65677.5/1024 =64.13 (gb)

Can i take 64.13GB as the tablespace size or my calculations are wrong.
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Prasanthhere

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Joined: 03 Aug 2005
Posts: 306

PostPosted: Tue Sep 23, 2008 4:51 pm    Post subject: Reply to: Tablespace Size Calc : Right or Wrong
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When I did the Volumetrics using a tool the tablespace size is coming only up to 96M

I don't think the table space size will be this much large (64.13 Gb) for JUst 982,782 records.

You need to take to your DBA to determinge the exact size specing the row count, row count growth, record length etc .
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sushanth bobby

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PostPosted: Tue Sep 23, 2008 5:30 pm    Post subject:
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Hi prasanth,
I googled & Googled, i got this link. Using this link i started my calculation. Is there any other way to calculate the size. Formulas anything... Is there any....

http://www.rwc.uc.edu/koehler/comath/42.html
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enrico-sorichetti

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PostPosted: Tue Sep 23, 2008 5:41 pm    Post subject: Reply to: Tablespace Size Calc : Right or Wrong
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You used some device characteristics which do not apply for example to 3390

I would stick to a simple count from the db2 side to get the bytes/Kbytes/Mbytes/Gbytes needed

and forget about the device geometry
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sushanth bobby

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PostPosted: Tue Sep 23, 2008 5:47 pm    Post subject:
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Enrico,

Quote:
You used some device characteristics which do not apply for example to 3390

My device type is also 3390 only. So, the calculations are entirely wrong.hmmmm..

Quote:
I would stick to a simple count from the db2 side to get the bytes/Kbytes/Mbytes/Gbytes needed

Are you talking about calculating like this.
Total number of records in the database * size of a single record.
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Prasanthhere

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Posts: 306

PostPosted: Wed Sep 24, 2008 10:46 am    Post subject: Reply to: Tablespace Size Calc : Right or Wrong
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Hi Sushanth,

First of all your calculation is wrong..

Quote:

67253760/1024 =65677.5(kb)
65677.5/1024 =64.13 (gb)


Actually the values would be like this only if I use your calcualtion

Code:

bytes 67253760
kilobytes 65677.5
megabits 513.10546875
megabytes 64.13818359375
gigabits 0.501079559326172


Means .5GB of space only and not 64.13

[/quote]
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sushanth bobby

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Joined: 29 Jul 2008
Posts: 1013
Location: India

PostPosted: Wed Sep 24, 2008 10:54 am    Post subject:
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Prasanth,

Oh my. I never thought, i would be making such a careless fundamental mistake. Thank You Very Much.....


Quote:
First of all your calculation is wrong..

You are telling my entire formula calculation is wrong, RIGHT.

And as enrico was telling table size can calculated by,
Code:
table size=row length*number of records.
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Prasanthhere

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PostPosted: Wed Sep 24, 2008 11:01 am    Post subject: Reply to: Tablespace Size Calc : Right or Wrong
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Quote:

You are telling my entire formula calculation is wrong, RIGHT


I was just mentioning that 64.13 GB was wrong
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sushanth bobby

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Joined: 29 Jul 2008
Posts: 1013
Location: India

PostPosted: Wed Sep 24, 2008 11:08 am    Post subject:
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Hi,

Ohh, OK.
Enrico was saying,
Quote:
You used some device characteristics which do not apply for example to 3390

Do you know anything about this..... Because, all these calculations are for oridinary Hard Disk.

Code:
16,384 cylinders/ disk
80 heads / cylinder
63 sectors / track
512 bytes / sector


Does mainframe use different type Hard Disks for their storage and their characteristic are entirely different.

Because, if this is true. My calculation will be WRONG.
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