• 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

You then issue the FILEDEF command to assign a CMS file identification
to the OS data set or DOS file so that CMS can read it. The format of
the FILEDEF command used for this purpose is: r r .,., r ., FIledef IDISK fn ft Ifmll IDSN ? I I l!lll IDSN q1 [q2 ••• ]1
L L ... .J L .J r r DISK Ifn ft Ifm'l IA11 I L L .J.J DUMMY r ., me.bernamel !CONCAT L .J
If you are issuing a FILEDEF for a DOS file, note that the OS prograa
that viII use the DOS file must have a DCB for it. For "ddna.e" in the
FILEDEF com.and line, use the ddname in that DCB. With the DSN operand,
enter the file-id of the DOS file. Soaetiaes, CMS issues the FILEDEF command for you. Although the CMS KOYEFILE co.aand, the supported CMS program product interfaces, and the CMS OPEN routine each issue a default FILEDEF, you should issue the
FILBDEF co •• and yourself to ensure the appropriate file is defined.
After you have issued the ACCESS and FILEDEF commands for an OS sequential or partitioned data set or DOS sequential file, commands (such as ASSEMBLE and STATE) can refer to the OS data set or DOS file
just as if it vere a CMS file. Several other CMS commands can be used vith as data sets and DOS files that do not reside on CMS disks. See the for a complete description of the CMS ACCESS, FILEDEF, LISTDS, MOYEFILE, QUERY, RELEASE, and STATE co.mands. For restrictions on reading OS data sets and DOS files under CMS, see
the The CMS FILEDEF comaand allows you to specify the I/O device and the
file characteristics to be used by a program at execution time. In
conjunction with the as simulation scheme, FILEDEF simulates the
functions of the data definition JCL statement.
FILEDEF aay be used only with programs using OS macros and functions.
For example:
filedef file1 disk proga data a1
After issuing this com.and, your program referring to FILE1 would access PROGA DATA on your A-disk.
2-46 IBM VM/370 System Logic and Program Determination--Volume 2