6.1.9 CICS System Program Interface and Exits

6.1.9.1 System Programming Commands

CICS system programming interface (SPI) commands provide you with the ability to access and modify CICS system information. SPI should be considered for CICS applications that presently modify and/or access CICS internal blocks. Although, SPI commands will not grant access to all CICS blocks and addresses, SPI commands either retrieve information about CICS resources or system elements from:

INQUIRE commands

COLLECT STATISTICS

or commands that modify the status or definition of the system or a resource, or invoke a system process:

SET commands

CREATE commands

DISCARD commands

PERFORM commands

ACQUIRE TERMINAL

or commands that modify or expand system execution by means of exits:

DISABLE PROGRAM

ENABLE PROGRAM

EXTRACT EXIT

RESYNC ENTRYNAME

CICS TS requires that all SPI commands specify an SP translator option and security checking for transactions issuing SPI commands. Therefore, you should review all SPI commands of CICS TS to determine what modifications and reassemblies are required to your present SPI programs. Please refer to CICS System Programming Reference, SC33-1689 for more details on SPI command changes and the CICS Application Programming Guide, SC33-1687 for information on the translator options.

6.1.9.2 Exits

Exits will require special attention and a significant amount of your conversion work effort. All exits will require a rewrite.

CICS TS does not support changes to internal control blocks. The user exit programming interface provides global user exit programs with access to some CICS services. It consists of a set of macro function calls that you can use in your user exit programs. It provides opportunities to extend CICS functions beyond the facilities provided in the standard CICS system, but it should be used with care. Any exit programs you write that use the interface must be written following the specific guidance documented in the CICS Customization Guide, SC33-1683, and you should carefully test to ensure that they cannot cause system errors.

The user exit programs must be in Assembler; the XPI is not provided for other languages. You should also note that programs containing XPI calls must be written to 31-bit standards, and must be reentrant.

Chapter 6. CICS 147

Page 171
Image 171
IBM OS/390 Cics System Program Interface and Exits, System Programming Commands, Collect Statistics, Acquire Terminal

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.