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Chapter 2: Files and Data Sets

This chapter provides introductory information on how Mainframe Express uses the following types of file:

2.1 Project Files

Within Mainframe Express a project is identified by the name of its project file. You specify the location and name of the project file (which has a file extension of .mvp) when creating a new project or opening an existing one.

Mainframe Express creates and updates the project file. You do not have to do anything with this file. Each project has a separate project file which a workgroup can share.

The Allocation folder field on the General page of the Catalog page on the Project Settings dialog box is initially set to the location of the project file. This field specifies the location for all other files created by Mainframe Express in the project, such as spooled output files. You can change this field to use another location.

When you first start Mainframe Express, you are asked to supply a user ID. This is used by Mainframe Express to identify who creates or updates cataloged files or the spool file.

2.2 System Catalog Files

Each project has a system catalog, which emulates the mainframe data set catalog. Mainframe Express uses the system catalog to hold information about the data sets used by its execution environment. You specify the location of the system catalog file (which has a default name of catalog.dat) when creating a new project. An existing file, created by another project, can be used. If the file does not exist, Mainframe Express creates it when the first data set is cataloged.

The location and name of the system catalog file is shown in the System catalog field on the General page of the Catalog page on the Project Settings dialog box. You can change this field to use a different system catalog file.

To maintain a connection with the mainframe environment, you can continue to use MVS data set names in JCL statements and TSO commands. However, these names have no meaning in a PC environment, so Mainframe Express also requires the name of the PC file that represents the data set. Both names are included in the catalog entry.

2.3 User Catalog Files

In addition to the system catalog, you can define one or more user catalogs for a project. These can be used in a similar way to the system catalog but are reserved for data sets with specific qualifiers. This enables you to build a catalog structure to suit your requirements.

You can define the user catalogs on the User page of the Catalog page on the Project Settings dialog box. For each user catalog, you will need to specify its location and name and the data set qualifier (node) associated with the catalog.

2.4 Data Set Files

This section contains basic information about using Mainframe Express with data sets. For further information on this subject, see the chapter Advanced Data Set Information in your IDE Technical Guide.

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

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

2.4.1 Partitioned Data Sets (PDS)

In an MVS mainframe environment, a file can be defined as an individual data set or as part of a partitioned data set (PDS). Mainframe Express supports both of these methods.

In a partitioned data set (organization = PO), the individual data sets are known as members (organization = PDSM). You define a partitioned data set and its members to Mainframe Express like any other data set. Procedure Libraries

Procedure libraries are partitioned data sets that contain procedures that can be specified in JCL jobstreams. Mainframe Express supports three types of procedure library and searches them in the following order.

  1. Libraries listed in a JCLLIB statement, which is specific to a job.

    You must allocate these libraries to the catalog.

  2. Libraries defined to Mainframe Express which are available for all projects and jobs.

    You can define up to eight of these libraries from the Workgroup View by right-clicking Dependency Libraries and clicking Add Dependency Folder on the popup menu.

  3. SYS1.PROCLIB library, which is specific to a catalog. Adding Files to a PDS

When you add an existing PC file into a partitioned data set, whether by the Add into PDS or the Add Members to PDS-name method (see Data Set Files), the file is added as a partitioned data set member (PDSM). A new catalog entry is created, and the PDSM inherits the properties of the PDS. Mainframe Express assigns an MVS data set name based on the PC filename, but you can rename it.

The Add into PDS method is restricted to PDSs that use a line sequential record format (such as procedure libraries). We recommend the Add Members to PDS-name method for adding multiple files into a PDS.

When you finish adding one or more files, the files are parsed to find any COPY and INCLUDE statements and to resolve any dependencies. They are shown by the Dependencies node on the Project View.

When you add a procedure file (with extension .prc), it is automatically added to the procedure library SYS1.PROCLIB. If the library does not exist, Mainframe Express first creates it and allocates it to the catalog.

2.4.2 System Log

When you run the first job in a project, Mainframe Express creates a system log file for that project and gives it an entry in the catalog. Mainframe Express updates this file with information about each job that is run. You can view and reset the system log from the Spool View.

By default, Mainframe Express uses the same name (MFMVS.SYSLOG) for the system log for all projects. This is shown in the System log dataset field on the Spool page of the Catalog page on the Project Settings dialog box. You can change this name for each project.

2.5 Spool Files

Mainframe Express emulates the spooler functions of the mainframe's job entry system. You can select emulation of either JES2 or JES3.

Mainframe Express creates a spool file for each of the following:

In Mainframe Express, a JCL jobstream can have only one job but the job can contain multiple job steps. You use an EXEC statement to specify the program to be executed by a job step. You can do this either directly:

EXEC PGM=program-name

or indirectly, using a cataloged procedure:

EXEC PROC=procedure-name ---------> EXEC PGM=program-name.

Although the Catalog View does not include spool files, they are assigned data set names.

If the data set name is not specified, the MVS name has the form:


If the data set is temporary, the MVS name has the form:



Note: You can also submit jobstreams for running on the mainframe and view the resulting spool output files in Mainframe Express. See the section Running a Job on the Mainframe in the chapter JCL Support.

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