PUT (QISAM) QISAK is not supported in CMS. PUTX PUTX support is provided only for data sets opened for QSAM-UPDATE with simple buffering. READ/WRITE (BISAM) BISAM is not supported in CMS. READ/WRITE (BSAM and BPAM) All the BSAM and BPAM options of READ and WRITE are supported except
for the SE option (read backwards).
READ (Offset Read of Keyed BDAM dataset)
This type of READ is not supported because it is used only for
spanned records. READ/WRITE (BDAM) All the BDAM and BSAM (create) options of READ and WRITE are
supported except for the Rand RU When an input or output error occurs, do not depend on OS sense
hytes. An error code is supplied by CMS in the ECB in place of the
sense bytes. These error codes differ for various types of devices and
their meaning can be found in the under DMS message 120S. The four methods of accessing BDAM records are:
1. Relative Block 2. Relative Track TIft 3. Relative Track and Key 4. Actual Address MBBCCHfiR The restrictions on these access methods are as follows: • Only the BDAM identifiers underlined above can be used to refer to
records, since CMS files have a two-byte record identifier. • CMS BDAM files are always created with 255 records on the first
logical track, and 256 records on all other logical tracks,
regardless of the block size. If BDAM methods 2, 3, or 4 are used
and the RECFM is U or V, the BDAM user .ust either write 255 records
on the first track and 256 records on every track thereafter, or he
must not update the track indicator until a NO SPACE FOUND message is
returned on a write. For method 3 (WRITE ADD), this message occurs
when no more dummy records can be found on a WRITE request. For methods 2 and 4, this will not occur, and the track indicator will be
updated only when the record indicator reaches 256 and overflows into
the track indicator. • Two files of the same filetype, both of which use keys, cannot be
open at the same time. If a program that is updating keys does not
close the file it is updating for some reason, such as a system failure or another IPL operation, the original keys for files that
are not fixed format are saved in a temporary file with the same filetype and a filename of $KEYSAVE. To finish the update, run the
program again.
2-44 IBM VM/370 System Logic and Program Determination--Volume 2

• Once a file is created using keys, additions to the file must not be made without using keys and specifying the original length. • The number of records in the data set extent must be specified using
the FILEDEF command. The default size is 50 records. • The minimum LRECL for a CMS BDAM file with keys is eight bytes.
READING as DATA SETS AND DOS FILES USING as MACROS CMS users can read OS sequential and partitioned data sets that reside
on OS disks. The CMS MOYEFILE command can be used to manipulate those data sets, and the OS QSAM, BPAM, and BSAM macros can te executed under CMS to read thea. The CMS MOYEFILE command and the same OS macros can also be used to manipulate and read DOS sequential files that reside on DOS disks. The OS macros handle the DOS data as if it vere OS data.
The following OS Release 20.0 BSAM, BPAM, and QSAM macros can be used
with CMS to read OS data sets and DOS files:
BLDL RDJFCB BSP FIND READ
CHECK GET SYNADAF CLOSE NOTE SYNADRLS DEQ POINT WAIT DEYTYPE POST CMS supports the following disk formats for the OS and OS/VS sequential and partitioned access methods: • Split cylinders • User labels • Track overflow • Alternate tracks
As in OS, the CMS of the BSP macro produces a return code of
4 when attempting to backspace over a tape mark or when a beginning of
an extent is found on an OS data set or a DOS file. If the data set or
file contains split cylinders, an attempt to backspace within an extent,
resulting in a cylinder switch, also produces a return code of 4.
Before CMS can read an OS data set or DOS file that resides on a non-CMS disk, you must issue the eMS ACCESS command to make the disk on which it
resides available to CMS. The format of the ACCESS command is: ACCESS cuu mode[/ext] You Must not specify options or file identification when accessing an OS or DOS disk. CMS Introduction 2-45