DEFRAG CONSOLIDATE not working?

[Pinnacle]

Running z/OS V1R8.  I've found that when I use CONSOLIDATE on my DEFRAGs, 
the DEFRAG doesn't work.  I had a run this morning where CONSOLIDATE 
actually increased the frag index, and then a subsequent DEFRAG without 
CONSOLIDATE dropped it considerably.  Here are the stats with CONSOLIDATE:


ADR208I (003)-EANAL(01), 2007.220 09:39:28 BEGINNING STATISTICS ON TOMM0B:
 FREE CYLINDERS 000788
 FREE TRACKS005800
 FREE EXTENTS   001258
 LARGEST FREE EXTENT (CYL,TRK) 36,
 FRAGMENTATION INDEX 0.688
 PERCENT FREE SPACE 11
ADR213I (003)-EANAL(01), 2007.220 09:41:42 ENDING STATISTICS ON TOMM0B:
 DATA SET EXTENTS RELOCATED 000503
 EXTENTS CONSOLIDATED   000504
 TRACKS RELOCATED   003856
 FREE CYLINDERS 000764
 FREE TRACKS006160
 FREE EXTENTS   001405
 LARGEST FREE EXTENT (CYL,TRK) 36,
 FRAGMENTATION INDEX 0.702

Here's what it looks like without CONSOLIDATE:

ADR208I (003)-EANAL(01), 2007.220 09:48:46 BEGINNING STATISTICS ON TOMM0B:
 FREE CYLINDERS 000764
 FREE TRACKS006155
 FREE EXTENTS   001404
 LARGEST FREE EXTENT (CYL,TRK) 36,
 FRAGMENTATION INDEX 0.702
 PERCENT FREE SPACE 11
ADR213I (003)-EANAL(01), 2007.220 09:52:56 ENDING STATISTICS ON TOMM0B:
 DATA SET EXTENTS RELOCATED 002181
 TRACKS RELOCATED   017080
 FREE CYLINDERS 001147
 FREE TRACKS000410
 FREE EXTENTS   61
 LARGEST FREE EXTENT (CYL,TRK) 001104,
 FRAGMENTATION INDEX 0.054

Any ideas on why this happens?  Does CONSOLIDATE not DEFRAG by design?

Regards,
Tom Conley

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Re: DEFRAG CONSOLIDATE not working?

[Patrick Lyon]

On Wed, 8 Aug 2007 11:53:39 -0400, Pinnacle 
[EMAIL PROTECTED] wrote:

Running z/OS V1R8.  I've found that when I use CONSOLIDATE on my 
DEFRAGs,
the DEFRAG doesn't work.  I had a run this morning where CONSOLIDATE
actually increased the frag index, and then a subsequent DEFRAG without
CONSOLIDATE dropped it considerably.  

From the DFDSS Administration Guide:

Notes: 


1. The process of combining data set extents can cause the freespace to be 
more fragmented than it was before the operation began. 

2. Despite the fact that DFSMSdss performs freespace defragmentation 
following the consolidation of data set extents, there is a possibility that 
the 
fragmentation index may be higher following a defrag operation with 
CONSOLIDATE specified than before the operation began. 

Source:
(Watch wrap)  http://publibz.boulder.ibm.com/cgi-
bin/bookmgr_OS390/BOOKS/dgt2u250/9.2?

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