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maintain the ″VSAM Ownership Bit″ in the VTOC, and the list of volumes owned
by the catalog.
Under VSE, multiple VSAM catalogs can own space on the same DASD volume,
as long as only one recoverable catalog owns space on that volume. This
support has been provided by adding a VSE unique ″bit map″ in the VSAM
catalog, identifying the space that is owned by a particular catalog, on a
particular volume. This is not supported with OS/390 VSAM. Only one VSAM
catalog can own VSAM space on a volume.
While OS/390 will prevent OS/390
jobs from creating this environment, it may not recognize shared volumes which
have been imported from VSE. This can lead to catalog or data set damage if
space is deleted, defined, or expanded under OS/390
. Refer to the
VSE/VSAM
Programmer
′
s Reference
, SC24-5145, Chapter 10 for additional information.
OS/390 ICF catalogs do not ″own″ volumes. ICF uses Basic Catalog Structure
(BCS) data sets, one per catalog, to contain catalog information. It uses VSAM
Volume Data Sets (VVDS), one per DASD volume, to contain information about
the VSAM data sets on that volume. Thus it′s possible to have multiple VSAM
data sets on the same volume that are cataloged in different ICF catalogs. It is
also possible to have more than one ICF catalog on a volume.
5.6.5.4 AMS Commands
DELETE IGNOREERROR
VSE/VSAM provides the ″DELETE... IGNOREERROR″ command to DELETE a
cluster that had been only partially deleted previously. OS/390 VSAM provides
this function for ICF catalogs using the ″DELETE... TRUENAME″ command. Also,
the OS/390 DELETE VVR and DELETE NOSCRATCH commands can be used to
delete partial VSAM structures.
SYNCHK Parameter
OS/390 AMS does not support the SYNCHK parameter. This was used to test
VSE AMS commands by allowing IDCAMS to syntax check the commands
without executing them. VSE AMS also supports other test and debugging
parameters which may not be applicable in the OS/390 AMS environment.
XXL KSDS (New in VSE/ESA 2.3, greater than 4GB KSDS)
OS/390 VSAM has provided support for VSAM data sets larger than 4GB in size
only for SMS managed data sets in extended format with the extended
addressability attribute. These data sets must be cataloged in ICF catalogs
because they are SMS managed. VSE/ESA Version 2.3 includes new VSAM
support for KSDS files only which are larger than 4GB. The implementations of
the two VSAM systems are not compatible, due to the differences between
VSAM catalogs used by VSE, and ICF catalogs used by OS/390. XXL data sets
defined in VSE will have to be unloaded from VSE and reloaded in OS/390.
COMPRESS (New in VSE/ESA 2.2, VSAM Record Compression)
OS/390 VSAM has provided support for compression of VSAM data sets only for
SMS managed data sets in extended format and Compaction set to Yes. These
data sets must be cataloged in ICF catalogs because they are SMS managed.
Chapter 5. Disk and Tape Storage Considerations 121