ACCESS METHODS SUPPORTED BY ces as access methods are supported, to varying extents, by CMS. Under CMS, you can execute programs that use the as data management macros that are
supplied for the access methods listed below.
, eMS Support for OS eMS Support for Real I Simulated Data Sets as Data Sets on as I Access Method on CMS Disks Disks I I BDAM Yes No I EPAM Yes Yes (read only) I BSAM Yes Yes (read only) I QSAM Yes Yes (read only) I VSAM No Yes I L----------------------------------------------------------------------J You can execute programs in C8S that read records
from as data sets using the BPAe, BSA8, or QSA8 access You cannot, however, write or update as data sets that reside on as disks. EDAM: eMS can neither read nor write as data sets on as disks using the BDAM access method. VSAM Files: CMS can read and write VSA8 files on as disks. InformatIon on using VSAM under CMS, see "Section 10. Using
Method Services and VSAM Under C8S and CMS/DOS." For
Access
If you want to test programs in CMS that create or modify as data sets,
you can write "aS simulated data sets." These are CMS files that are
maintained on CMS disks, but in as format rather than in CMS format. Since they are CMS files, you can edit, rename, copy, or manipulate them just as you would any other eMS file. Since they are in OS-simulated format, files with variable-blocked records may contain block and record
descriptor words so that the access methods can manipulate them properly.
The files that you create from as programs do not necessarily have to
be as simulated data sets. You can create C8S files. The format of an
output file depends on how you specify the filemode number when you
issue the FILEDEF command to identify the file to CMS. If you specify
the filemode number as 4, eMS creates a file that is in as simulated
data set format on a CMS disk. CMS can read and write as simulated data sets using the BDAM, ESAM, and QSAM access methods. When an input or output error occurs, do not depend on as sense
bytes. An error code is supplied by eMS 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 OMS message 120S. 130 IBM VM/370 eMS User's Guide
Page of GC20-1819-2 As Updated April 27, 1981 by TNL SN25-0828 For 5748-XE1 The following restrictions apply when you read OS data sets from OS disks under eM S: • Read-password-protected data sets are not read.
t • RACF password protection is ignored • BDAM and ISAM data sets are not read. • Multivolume data sets are read as single-volume data sets.
End-of-volume is treated as end-of-file and there is no end-of-volume
switching. • Keys in data sets with keys are ignored; only the data is read. • User labels in user-labeled data sets are bypassed (except for user
standard labels on tapes). See "Tape Labels in CMS" for details. • Results may be unpredictable if two DCBs access the same data set at
the same time.
Using the FiLEDEF Command Whenever you execute an as program under CMS that has input and/or
output files, or you need to read an as data set onto a CMS disk, you
must first identify the files to CMS with the FILEDEF command. The
FILEDEF command in CMS performs the same functions as the data
definition (DD) card in as job control language (JeL): it describes the
input and output files. When you enter the FILEDEF command, you specify: • The ddname • The device type • A file identification, if the device type is DISK • Type of label on your tape file, if tape label processing is
specified • Options (if necessary) Some guidelines for entering these specifications follow. SPECIFYING THE DDNAME
If the FILEDEF command is issued for a program input or output file,
then the ddname must be the same as the ddname or file name specified
for the file in the source program. For example, you have an assembler language source program that contains the line:
INFILE DeB DDNAME=INPUTDD, MACRF=GL, DSORG=PS,RECFM=F,LRECL=80 For a particular execution of this program, you want to use as your
input file a CMS file on your A-disk that is named MYINPUT FILE, then, you must issue a FILEDEF for this file before executing the program: Section 8. Developing OS Programs Under CMS 131
Previous Page Next Page