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Modern disk arrays are still regarded by the z/OS operating system as
a set of conventional DASD volumes. Each logical volume in the array
has a fixed number of cylinders, and space is managed in
the usual way – with a standard VTOC and VTOCIX. As such, the reasons
for re-organizing a DASD volume are, for most z/OS installations,
as valid today as they have always been...
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| Many disk volumes have small non-contiguous areas of free
space spread haphazardly throughout the volume. Although the primary
allocation of a new data set can be satisfied in multiple extents, if
no single free space extent is large enough, this may force the data
set to be allocated from two or more non-contiguous free areas. |
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FASTCPK can
quickly consolidate free space on a
volume into as few as one or two contiguous areas. |
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| Either through natural growth or inaccurate
space estimates, data sets often grow beyond their original allocated size.
They may end up occupying up to 123 extents and it may become impossible to
extend the data set even though a large amount of free space is still available
on the volume. This leads to the creation of multi-volume data sets, which have
their own special set of requirements (e.g. on backup and restore). |
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FASTCPK
can merge the extents of Sequential, PDS, PDSE, VSAM, DB2 and Extended
Format VSAM data sets. |
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| Some data sets on a volume may occupy a larger
data space than necessary. This can be caused by inaccurate space estimates
or a reduction of the amount of data in the data set. The unused space within
these data sets is not available for allocation to other data sets. |
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FASTCPK
can release all or part of the unused space within Sequential, PDS,
PDSE, VSAM, DB2 and extended Format VSAM data sets. |
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| Hardware and software system failures can lead
to inaccurate VTOCs, which do not reflect the true status of the volume
on which they reside. |
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FASTCPK
can analyze a VTOC to detect (and in most cases fix) logical errors, such
as invalid F5 DSCBs and incorrect free space definitions. |
The example below illustrates the use of FASTCPK to do a Space Release
and Compaktion across all online DASD volumes with volsers beginning “TSO” and “TEST”.
- The first step releases free space from all inactive PS, PO, and VSAM data sets.
- The second step does a FASTCPK on any volume where there are more than 20
free space areas. Any active datasets at the time of the Compaktion will not be moved.
- Although the release and compaktion tasks can be done in a single step, the 2-step
technique shown below is faster because the FASTCPK step will move fewer tracks than the
single-step job.
//RLSE EXEC PGM=FDRCPK,REGION=0M
//SYSPRINT DD SYSOUT=*
//SYSMAP DD SYSOUT=*
//SYSIN DD *
COMPAKT TYPE=RLSE,VOL=(TSO*,TEST*),
PSRLSE=ALL,PORLSE=ALL,VSRLSE=ALL,NOSECOND=NORLSE
/*
//FASTCPK EXEC PGM=FDRCPK,REGION=0M,COND=EVEN
//SYSPRINT DD SYSOUT=*
//SYSMAP DD SYSOUT=*
//SYSIN DD *
COMPAKT TYPE=FASTCPK,VOL=(TSO*,TEST*),
CPKFREEX=20,LOG=YES,UNABLE=IGNORE
/*
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| Can we HELP you... |
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Looking for more information?
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Visit us at:
IBM System z
TECHNICAL UNIVERSITY
2010
October 4-8, 2010
Boston, MA
Booth#: 20
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