Command CICS

Last updated
Command CICS
Developer(s) Ken Dakin
APT Ltd, UK
Initial release1993
Stable release
n/a / 1 January 1993;26 years ago (1993-01-01)
Operating system MVS, MVS/XA, MVS/ESA, DOS/VSE
Platform IBM/370, IBM ES/9000 family, z/OS & compatibles
Type Emulator
License Proprietary software
Websiten/a

Command CICS or Command-CICS is a software product that allows organizations to migrate from "Macro level" CICS to "Command level" CICS without any re-programming so that companies could migrate to later versions of CICS that did not support macro level application programs. [1] The later versions of CICS offered many advantages over previous versions yet tens of thousands of application programs were effectively locked out of the new version unless they were prepared to operate two completely different versions of CICS on the same Operating Systems, creating both operational and maintenance problems. Two different, simultaneous, CICS Licenses were also required.

CICS transaction management system by IBM

Customer Information Control System (CICS) is a family of mixed language application servers that provide online transaction management and connectivity for applications on IBM mainframe systems under z/OS and z/VSE.

Contents

History

When CICS was first released by IBM in the late 1960s, it used IBM Assembler macros to generate the API system calls to the CICS teleprocessing monitor kernel. This was also true even if programs were written in COBOL or PL/1. Ken Dakin an independent programmer and CEO of APT Ltd. in the U.K., realized that by creating a middleware product, the problem could be solved for almost all situations. Ken Dakin approached IBM to market his product but received no interest at the time, despite the fact that tens of thousands of their clients application programs would need to be converted or rewritten for the new versions of CICS, costing many millions of dollars.

IBM American multinational technology and consulting corporation

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A teleprocessing monitor is a control program that monitors the transfer of data between multiple local and remote terminals to ensure that the transaction processes completely or, if an error occurs, to take appropriate actions.

Macro level emulation

Command-CICS intercepted macro level applications via a Link-edited (static) "stub" positioned ahead of the Load module (MVS) or Phase (DOS/VSE). On gaining control from the CICS Program Control Program (PCP), a "pseudo macro level" environment was established consisting of a pointer to a (unique) pseudo "Common System Area" (CSA), a pointer to a Transaction Control Area plus Transaction Work Area (TCA+TWA) and a pseudo Terminal Control Terminal Entry (TCTTE) and other artifacts of a macro level environment. Before passing control directly to the original program entry point, Command-CICS set up the actual general purpose registers, R13 and R12 to point to the pseudo control blocks. The CSA was the principal control block holding pointers to the CICS kernel programs (File Control Program, Storage Control Program etc.) in a real macro level CICS environment. The Command-CICS CSA had alternative pointers to Command-CICS entry points instead. It was possible to use CEDF to debug the application program calls when Command-CICS was used.

MVS operating system for IBM mainframes

Multiple Virtual Storage, more commonly called MVS, was the most commonly used operating system on the System/370 and System/390 IBM mainframe computers. It was developed by IBM, but is unrelated to IBM's other mainframe operating systems, e.g., VSE, VM, TPF.

Macro interface

The application program proceeded to execute normal machine code instructions right up to its first macro level API call, thus adding zero overhead to the program until that point. As soon as the API call left the application program, Command-CICS code would gain control and replace the original linkage with its own, equivalent, Command-level call. In original earlier command level CICS versions (that supported both Macro and Command level programs), the CICS "Exec Interface Program" (DFHEIP) converted the Command level call to an 'actual macro level call. This would add a very small additional overhead only during CICS calls. Later versions of CICS, however, executed the CICS API directly, imposing no additional "backward compatibility" overhead.

Marketing

Command-CICS was initially sold by APT Ltd in the U.K. and APT International in mainland Europe and the rest of the world. At the present time CommandCICS is being offered by Advanced Software Products Group, Inc. of Naples, Florida, United States

Florida U.S. state in the United States

Florida is the southernmost contiguous state in the United States. The state is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Atlantic Ocean, and to the south by the Straits of Florida. Florida is the 22nd-most extensive, the 3rd-most populous, and the 8th-most densely populated of the U.S. states. Jacksonville is the most populous municipality in the state and the largest city by area in the contiguous United States. The Miami metropolitan area is Florida's most populous urban area. Tallahassee is the state's capital.

Competition

CICS/COMET for z/OS - a similar product from UNICOM Systems Inc. [2] Adds some overhead (because of the requirement to dynamically add a stub).

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References

  1. ↑ "IBM - Command/CICS". ibm.com.
  2. ↑ "UNICOM Systems, Inc. -- A Division of UNICOM Global :: CICS/COMET for z/OS". unicomsi.com.
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