CICS APIThis chapter explains Mainframe Subsystem Support.
Mainframe Subsystem Support (MSS) enables you to maintain and run CICS, IMS and JCL applications. These applications have been migrated from the mainframe and now run under reUZE Server.
You use reUZE Developer for maintaining your CICS, IMS and JCL applications. If you are working with CICS, you can edit and compile BMS maps, and also compile the CICS programs, using the Micro Focus CICS preprocessor, which translates the CICS commands into native code. If you are working with IMS, you can edit and generate your DBDs, MFSs and PSBs, and compile your IMS programs. If you are working with JCL, you can edit and create JCL, and build projects containing the programs that the JCL references. When the application is ready to run, you then deploy it to reUZE Server.
You use reUZE Server for running your CICS, IMS and JCL applications, for testing and for production use. reUZE Server also provides facilities for monitoring and controlling your applications and for other tasks such as maintaining CICS resource definitions and viewing the system catalog and spool queues.
System integrators are typically responsible for migrating the CICS, IMS and JCL applications from the mainframe. They download the applications, and leave you with a working application, running under reUZE Server.
In some cases the system integrators might use Micro Focus Mainframe Express to migrate your CICS or IMS applications. They replace one mainframe-only language or technology at a time, and make sure that the application works correctly on Mainframe Express before continuing. For example, if your application includes Assembler and PL/I modules, they might replace the Assembler modules with COBOL modules. They would then recompile and test the application thoroughly before moving on to replace the PL/I modules.
When the system integrators have got the application up and running under reUZE Server, they hand over to you to maintain and develop the applications in reUZE Developer, and to run the applications under reUZE Server
This book assumes that your application has been migrated from the mainframe, and that it runs successfully under reUZE Server.
When the CICS application has been migrated from the mainframe to the PC, you maintain and develop the application as follows:
If your client program uses a graphical or Web interface, use the IBM External Call Interface (ECI) to communicate with the CICS application.
If your application uses Basic Mapping Support (BMS) mapsets, which provide the user interface, you might need to update these. The BMS Screen Painter in Net Express enables you to do this.
The client program for your CICS application need not use BMS. You can have a graphical/ Web user interface that is written in Java or runs under Microsoft .NET. In this case you use the IBM External Call Interface (ECI) to communicate with the CICS application.
You use ECI calls in your client program to communicate with the CICS application running under Enterprise Server. The ECI calls from your client program are passed through the IBM CICS Transaction Gateway to reUZE Server.
For an example of using an ECI client, see the chapter Legacy Extension with MSS in your Mainframe Subsystem Support Configuration and Administration Guide.
A large subset of the command-level API of IBM CICS is supported and provides the expected behavior for programs written using this syntax. Most syntax that is not functionally supported is recognized so that programs using these commands and operands will compile without change. Much of the CICS system programming interface is also supported; some CICS APIs in MSS return fixed, default values, rather than values that the mainframe might return.
Data access is supported for data in emulated VSAM files, IMS databases, and relational database systems.
VSAM file emulation is supported for ESDS and RRDS files and KSDS data sets, which can also be shared with non-CICS (batch) applications. Fileshare provides data integrity for VSAM emulation for application data files, temporary storage and transient data queues. Alternate indexes are supported for application data files. Emulated VSAM files use standard Micro Focus file formats.
Support is provided to the XA-compliant SQL databases from Oracle and IBM DB2/UDB.
The CICS command syntax is recognized by a preprocessor, which runs as part of the program compilation step. The preprocessor scans the program source for EXEC CICS commands and replaces them with native statements for the language in which the program is written.
You invoke the precompiler, ECM (External Compiler Module), by using the Compiler directive CICSECM().
When the IMS application has been migrated from the mainframe to the PC, you maintain and develop the application as follows:
When the JCL application has been migrated from the mainframe to the PC, you maintain and develop the application as follows:
File and database support is the same as for CICS applications.
When the CICS, IMS or JCL application has been compiled, you run it under reUZE Server. If you have CICS, IMS or JCL applications already running under an enterprise server, you might be able to use that enterprise server. Alternatively, if you want to run the application on your own machine under your own enterprise server, you need to configure an enterprise server for running CICS, IMS or JCL applications.
The Enterprise Server Administration console and Enterprise Server Monitoring and Control (ESMAC), provide facilities to do this. Among other tasks, you need to:
For more information see the chapters Administering CICS-enabled Enterprise Servers , Administering JCL-enabled Enterprise Servers Administering IMS-enabled Enterprise Servers in your Mainframe Subsystem Support Configuration and Administration Guide.
The resources that your CICS application uses need to be defined, so that you have a CICS environment in which you can run and debug your applications. The resource definitions are set up as part of the migration of your application from the mainframe. They are stored in a Resource Definition file called dfhdrdat.
IMS and JCL applications also use CICS-style resource definitions, defined in the dfhdrdat file.
The resource definitions include:
The SIT defines the initialization parameters to use when the enterprise server that runs your application is started. You might need to change some of these parameters for your project.
A SIT is required for CICS, IMS and JCL applications.
The startup list contains the list of the groups of resources to be used. reUZE Server loads all the groups in the startup list. The base startup list dfhlist contains recommended system groups that you should include in all your user-defined startup lists.
A startup list is required for CICS, IMS and JCL applications.
Resource groups are sets of resource definitions that define the programs and files that are used by the enterprise server running your application. If you create any resource groups you need to add them to the startup list, or you can add them at execution time in Enterprise Server with the CINS supplied transaction.
Resource groups for CICS include:
The only resource group you need for JCL is a JES resource group. This contains definitions of special service execution processes which start when the enterprise server is started, and which run JCL jobs and handle the sending of job output to a printer.
IMS applications also need to use the JES resource group, as it contains definitions of the message processing regions (MPRs) which start when the enterprise server is started.CICS applications on the mainframe run with an EBCDIC character set. PCs use an ANSI character set. When CICS applications are migrated from the mainframe, the majority of them are converted to use ANSI or ASCII, and they run under Enterprise Server using ANSI or ASCII. However, there are some cases where an application needs to continue to use EBCDIC on the server, while the client program uses ANSI or ASCII. In these cases, you need to set up data conversion macros to ensure the data is converted.
For details see the section Data Conversion in the chapter Legacy Extension with MSS in your Mainframe Subsystem Support Configuration and Administration Guide
CICS applications can operate over networks in client/server, cooperative, and distributed processing modes.
The supported CICS intersystem communication facilities include:
For more information about using these facilities, see the chapter Legacy Extension with MSS in your Mainframe Subsystem Support Configuration and Administration Guide.
The user interface to CICS and IMS applications from the PC is often through 3270 terminal emulators. The 3270 terminal emulators enable the CICS and IMS applications to display input and output screens on the PC using 3270 data streams and to receive input from the PC. It is intended for programs that use BMS or build 3270 data streams. Emulation is provided for 3270 models 2 through 5.
We recommend that you use a Telnet 3270 (TN3270) client. The keyboard mapping and support for character level attributes is a property of the third-party TN3270 client you choose.
When you start a 3270 terminal emulator, it is separate from the enterprise server that runs the CICS or IMS application. Terminals do not need to be predefined. This means terminal emulation characteristics can be specified at terminal startup.
reUZE Server needs to have a listener for requests from 3270 terminal emulators. You add this as part of configuring the enterprise server that will run your CICS or IMS application.
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