Data Set Files

This section contains basic information about using MSS with data sets. For further information on this subject, see the chapter Advanced Data Set Information.

All data sets that are referenced in JCL statements or TSO commands must have an entry in the catalog so that MSS can locate the local file that represents the data set. These data sets include:

Cataloged procedures referenced by EXEC statements
JCL procedures referenced by INCLUDE statements or TSO SUBMIT commands
Input and output data sets referenced in DD statements supported by MSS. See the section JCL Features in the chapter JCL Support for more information.
Input and output data sets referenced in TSO ALLOCATE, FREE and DELETE commands
REXX execs referenced by TSO EXEC commands
Partitioned data sets (libraries) that contain any of the above data sets

On the mainframe, data sets can be either cataloged or uncataloged. You can locate cataloged data sets using their catalog entry, and locate uncataloged data sets using their VOLUME number. In the Windows and UNIX environments, you cannot use the VOLUME to map physical locations as you can on the mainframe. Therefore, we catalog all data sets on Windows and UNIX. The catalog entry for every data set contains a flag that indicates whether a data set is cataloged or uncataloged; however, all data sets, both cataloged and uncataloged, are actually located using the catalog.

When viewing the catalog you can choose to see just the cataloged data sets or to see both the cataloged and uncataloged data sets.

Data sets that are not referenced in JCL statements or TSO commands do not need entries in the catalog. For example, you can write a program that accesses a file that has no entry on the system catalog by specifying its physical filename in the SELECT clause in the Environment division.

There are three methods of including an entry in the catalog:

New on the Catalog page in ESMAC
Click New on the Catalog page in ESMAC. You need to specify both the MVS name and the local physical filename.
Through the allocation of a new data set (DISP=NEW or DISP=MOD for a new file) by means of a DD statement in a jobstream or an ALLOCATE command in REXX exec. MSS assigns the physical filename.
Dynamically, by MSS, if a data set is used which does not already have an entry. MSS assigns the physical filename.

When MSS assigns the physical filename, it uses the default data file path set on the Properties > JES page of ES Admin, followed by the mainframe name with the extension .dat, For example, if the default path for data files is c:\catalog\data sets then a file with an MVS name of MFE2004.S1217.S160553.J01013.D00006.SYSOUT, will be stored locally as C:\CATALOG\data setS\MFE2004.S1217.S160553.J01013.D00006.SYSOUT.DAT

Note: Default behavior is to allow new data sets to be cataloged without specifying a SPACE parameter. If you prefer that JCL missing the SPACE parameter fails in the same way it does on the mainframe, set the MF_NEWSPACE=Y environment variable.