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Table space extents > 1 , Table contains 0 Rows.

 
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gylbharat

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Joined: 31 Jul 2009
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Location: Bangalore

PostPosted: Mon Oct 22, 2012 2:30 pm    Post subject: Table space extents > 1 , Table contains 0 Rows.
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Hi,

I have created a segmented tablesspace with only One table in that that tablespace.

However I observed something strange, Tablespace has extents 5 even if the table is empty (Zero Rows).

Can any one explain this?
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enrico-sorichetti

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PostPosted: Mon Oct 22, 2012 4:12 pm    Post subject: Reply to: Table space extents > 1 , Table contains 0 Rows
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probably an allocation <feature> ...
is the total space allocated equal to the initial space request
if yes then the volume has a fragmentation issue

generally , unless specifically requested, there is no guarantee that the initial allocation will be satisfied with a <single> extent
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gylbharat

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PostPosted: Mon Oct 22, 2012 4:24 pm    Post subject:
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Sorry... I didnot get you completely... Are you saying... say I request Primary Quantity as 100 Cyls , there was not enough space in any volume (STORAGE Group) which could allocate 100 Cyls in Single Extent?

Please let me know if this understanding is correct. In such cases how do I make sure it spans in 1 Extent?
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enrico-sorichetti

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PostPosted: Mon Oct 22, 2012 4:36 pm    Post subject: Reply to: Table space extents > 1 , Table contains 0 Rows
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Yes, I do not remember the exact sequence for the choice of eligible volumes

1) search for a volume with the total space requested available
2) search for a volume with the total space requested available in a single extent
at a certain point as many extents needed will be allocated

if <requested> and no contiguous space is available You will get IIRC a jcl error

are You defining the CLUSTER or are You letting DB2 do it under the covers ?
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gylbharat

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PostPosted: Mon Oct 22, 2012 4:38 pm    Post subject:
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Quote:
are You defining the CLUSTER or are You letting DB2 do it under the covers ?


We are not defining the table index to be clustered. As by default 1st index will act as clustering index.

How we can make it to 1 Extent?
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enrico-sorichetti

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PostPosted: Mon Oct 22, 2012 4:49 pm    Post subject: Reply to: Table space extents > 1 , Table contains 0 Rows
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Quote:
We are not defining the table index to be clustered. As by default 1st index will act as clustering index.


CLUSTER as per VSAM definition

a VSAM object is not called a file ...
is called a CLUSTER ...
with a DATA component and when needed an INDEX component

the relations between CLUSTER DATA INDEX ( primary/alternate ) PATH are called ASSOCIATIONS

the big entity consisting of
BASE CLUSTER, ALTERNATE INDEXES, PATH
is sometimes called a SPHERE

all is explained ..

here
z/OS V1R13.0 MVS JCL User's Guide
http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/iea2b570/CCONTENTS?SHELF=all13be9&DN=SA22-7598-07&DT=20110610095749
z/OS V1R13.0 MVS JCL Reference
http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/iea2b6b1/CCONTENTS?SHELF=all13be9&DN=SA22-7597-16&DT=20120814180937

and ...
z/OS V1R13.0 DFSMS Introduction
http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/DGT2DI40/CCONTENTS?SHELF=dgt2bkb1&DN=SC26-7397-04&DT=20110525151606
z/OS V1R13.0 DFSMSdfp Storage Administration
http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/DGT2S2A1/CCONTENTS?SHELF=dgt2bkb1&DN=SC26-7402-16&DT=20120126150025
z/OS V1R13 DFSMS Using Data Sets
http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/DGT2D4A0/CCONTENTS?SHELF=dgt2bkb1&DN=SC26-7410-11&DT=20110606092005


but also in the IBM REDBOOKS
here
http://www.redbooks.ibm.com/abstracts/sg246366.html

and in the series
ABCs of z/OS System Programming
( link to the first of it )
http://www.redbooks.ibm.com/abstracts/sg246981.html
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gylbharat

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PostPosted: Mon Oct 22, 2012 5:14 pm    Post subject:
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I am creating DB2 managed tablespaces. No I dont have control on defining LDS.
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