In OS/390 Language Environment a sample job, CEEWHLLX, is provided that contains an SMP/E USERMOD to replace the IBM-supplied HLL user exit with your HLL user exit.

17.5.2.3 Abnormal Termination Exits

Language Environment provides the ability to invoke an abnormal termination exit before it terminates a thread due to an unhandled condition of severity 2 or greater. This allows an abnormal termination exit to collect problem determination data before Language Environment frees the resources it has acquired.

Abnormal termination exits can be invoked in CICS or non-CICS. You can code your own abnormal termination exits. In LE/VSE this is described in the LE/VSE Installation and Customization Guide. In OS/390 Language Environment this is described in OS/390 Language Environment Customization.

In OS/390 Language Environment (as with LE/VSE 1.1) no default or sample abnormal termination exits are supplied.

17.5.2.4Abnormal Termination Exits and LE/VSE 1.4 and Later Releases

In LE/VSE 1.4 and later releases, default abnormal termination exits are supplied. These are CEEBDATX for batch and CEECDATX for CICS. CEEBDATX is a null module that immediately returns to the caller when invoked. CEECDATX issues abend 4039 when an unhandled condition occurs of severity 2 or greater.

In LE/VSE 1.4 and later releases, sample source programs are supplied that can be used as examples of how to write an abnormal termination exit. These are CEEBBATX.A and CEEBNATX.A. CEEBBATX.A is a batch abnormal termination exit that produces a system dump when invoked. CEEBNATX.A is a batch or CICS exit that does nothing but return to the caller when invoked.

17.5.3 Callable Services and Math Services

All LE/VSE callable services and math services are also provided in OS/390. The use of callable and math services in OS/390 Language Environment is described in the OS/390 Language Environment Programming Reference.

If you use LE/VSE callable services, there is one important fact of which you should be aware. Some LE/VSE callable services have names beginning with CEE5. The corresponding OS/390 Language Environment callable services have names beginning with CEE3. For example, the callable service in LE/VSE, to set the heading displayed at the top of the options report, is CEE5RPH. The corresponding OS/390 Language Environment callable service is CEE3RPH.

There are 14 such callable services. They are listed in Figure 56 on page 366. If you have used any of these callable services in your programs, you must change their names in your source code when you transfer the code to OS/390, and you must recompile your source code there. You cannot use the OS/390 Language Environment names in your VSE/ESA code, you cannot use the LE/VSE names in your OS/390 Language Environment code, and you cannot ship the compiled object code from VSE/ESA to OS/390 for link-editing there.

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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.
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