functions are provided by the Application Support Facility for MVS (ASF), 5685-043.

Some CICS programs written in assembler language may have to be reworked. These applications are more prone to violate the CICS API restrictions.

Also, be sure to review all EXEC CICS commands for changes in VALUES.

The name of the CSECT within module DFHECI changed from DFHECI to DFHELII. So, be sure that your LINKEDIT included DFHECI.

An application program that passes the address of a COMMAREA to another application program can be above 16MB, below 16MB, or it can be a zero address. A COMMAREA can be in CICS-key storage or USER-key storage (if CICS is running with storage protection), or in read-only storage (possibly obtained using an MVS GETMAIN call). The length of the COMMAREA can be a positive value or zero, but a negative value always results in an error. Therefore, the user must provide a condition check for a negative value in the user programs.

Any Assembler programs which use the DFHEISTG copybook should be reviewed. It increased by 136 bytes.

If you have any Distributed Transaction Processing (DTP) applications that use CICS APPC commands, changes to the CICS implementation of the APPC architecture could mean you need to change the APPC applications before you can migrate them to CICS TS.

Please review the CICS/ESA Distributed Transaction Programming Guide, SC33-1174 for more details.

CICS supports the following Assembler, COBOL, PL/I, and C/370 compilers:

High Level Assembler/MVS & VM & VSE Version 1.1 (5696-234) IBM PL/I for MVS & VM (5688-235)

OS PL/I Optimizing Compiler Version 2 Release 1 (5668-910)

OS PL/I Optimizing Compiler Version 1 Release 5.1 (5734-PL1), or later IBM COBOL for MVS & VM (5688-197)

VS COBOL II (5668-958 and 5688-023) IBM C/C++ for MVS/ESA (5655-121) C/370 (5688-040 and 5688-187).

CICS also supports IBM Language Environment for MVS run-time environment (5688-198), with the following SAA AD/Cycle COBOL, C/370, and PL/1 SAA AD/Cycle compilers:

SAA AD/Cycle COBOL/370 (5688-197)

SAA AD/Cycle C/370 (5688-216)

SAA AD/Cycle PL/I (5688-235).

Below are recommended conversion aids available to assist you with the conversion of your CICS application programs.

The DFHMSCAN utility program, which is available with CICS/VSE is recommended for reviewing CICS application program libraries. This program can be run against VSE application libraries to find out which application

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IBM OS/390 manual SAA AD/Cycle COBOL/370 SAA AD/Cycle C/370 SAA AD/Cycle PL/I

OS/390 specifications

IBM OS/390, a versatile operating system, was a cornerstone in enterprise environments and played a pivotal role in mainframe computing. Released in the mid-1990s, OS/390 combined the strengths of IBM's MVS (Multiple Virtual Storage) with new features and enhancements, targeting scalability, reliability, and performance in demanding business applications.

One of the key features of OS/390 was its robust support for multiple users and processes. The system allowed thousands of concurrent users to access applications and data, ensuring high availability and minimizing downtime—a critical requirement for many large organizations. This scalability was supported through various enhancements in memory management and processor scheduling, enabling optimal resource allocation across diverse workloads.

OS/390 was known for its superior workload management capabilities. The Workload Manager (WLM) component allowed administrators to define service policies, specifying how system resources would be allocated according to the priority of tasks. This ensured that critical business processes received the necessary resources while less critical tasks were managed more flexibly.

Another significant characteristic of OS/390 was its commitment to security. The operating system provided comprehensive security features, including user authentication, data encryption, and auditing capabilities. This focus on security was vital for organizations handling sensitive data, ensuring compliance with regulations and safeguarding against unauthorized access.

OS/390 also supported advanced technologies that facilitated integration and development. The system included features like the IBM CICS (Customer Information Control System) for transaction processing and IMS (Information Management System) for database management. These technologies allowed organizations to build robust, high-performance applications tailored to specific business needs.

The ease of network integration was another strength of OS/390. With the advent of the Internet and global connectivity, OS/390 systems could easily interface with various network protocols, enabling businesses to operate in a connected world. This inclusion paved the way for many organizations to expand their capabilities and offer new services, driving digital transformation.

In conclusion, IBM OS/390 represented a significant advancement in mainframe technology, combining scalability, security, and robust workload management. Its rich feature set and support for critical enterprise applications solidified its role as a vital component of many organizations' IT infrastructures, ensuring they could meet their operational challenges head-on while supporting future growth. As technology continues to evolve, the legacy of OS/390 remains influential in the realm of computing.