April 1, 1981
TheCMS/DOS shared segment contains the B-transients that are
simulated forDOS support in CMS. Three B-transients that pertain only
toVSAM are included in the VSAM saved segment: $$BOMSG1, $$BOKSG2, and
$$BENDQB. The $$BENDQB transient is calledby the ENQB macro and
releasedby the DEQB macro. Storage Requirements
TheVSAM and Access Method Services support in CMS requires both DASD
space and virtual storage.
TheVSAM and Access Method Services support adds approximately 2K to
the size of theCMS nucleus. In addition, this support uses free
storaqe to execute theDOS/VS logical transients and for buffers and
work areas.VSAM issues a GETVIS macro to request free If the CMS/DOS environment is invoked with the VSAM option
SETDOS ON (VSAM part of the CMS/DOS virtual storage is set aside for VSAM use.
Disk storage requirements vary depending upon device type:
Number of cylinders Required
DeviceUsg OS User 2314- 10 --20- 2319 10 20 3330 Model 1 6 12 3330 Model 11 6 12 3340 15 30 3344 15 30 3350 3 6
DataSet Compatibility Considerations CMS can read and update VSAM data sets that were created under DOS/VS or OS/VS. In addition, VSAM data sets created under CMS can be read and
updated byDOS/VS or OS/VS. However, if you perform allocation on a minidisk in you cannot
use that minidisk in anOS virtual machine in any manner that causes
further allocation.DOS/VS VSAM (and, thus, CMS) ignores the format-5,
free space, DSCB, onVSAM disks when it allocates extents. If
allocation later occurs in anOS machine, OS attempts to create a
format-5 DSCB. However, the format-5 DSCB created byOS does not
correctly reflect the free space on the minidisk. In eMS, allocation
occurs whenever data spaces or unique data sets are defined. Space is
released whenever data spaces, catalogs, and unique data spaces are
deleted.ISAM Interface Program (liP) CMS does not support the VSAM ISAM Interface Proqram (lIP). Thus, any
program that creates and accessesISAM (indexed sequential access
method) data sets cannot be used to accessVSAM key sequential data
sets. There is one exception to this restriction. If you have (1)OS PL/I programs that have files declared as ENV(INDEXED) and (2) if the library routines detect that the data set being accessed is a VSAM data
set, your programs will executeVSAM I/O requests.
312IBM VM/370 System Proqrammer's Guide
The
simulated for
to
$$BENDQB. The $$BENDQB transient is called
released
The
space and virtual storage.
The
the size of the
storaqe to execute the
work areas.
SET
Disk storage requirements vary depending upon device type:
Number of cylinders Required
Device
Data
updated by
use that minidisk in an
further allocation.
free space, DSCB, on
allocation later occurs in an
format-5 DSCB. However, the format-5 DSCB created by
correctly reflect the free space on the minidisk. In eMS, allocation
occurs whenever data spaces or unique data sets are defined. Space is
released whenever data spaces, catalogs, and unique data spaces are
deleted.
program that creates and accesses
method) data sets cannot be used to access
sets. There is one exception to this restriction. If you have (1)
set, your programs will execute
312