Table 43 (Page 2 of 2). Option Recommendations Differing between

LE/VSE 1.4 and OS/390 Language Environment

Language

Option

Recommendation

 

 

 

PL/I

ABTERMENC

RETCODE

 

 

 

 

DEPTHCONDLMT

0

 

 

 

 

STACK

128K,128K,BELOW,KEEP

 

 

 

 

TERMTHDACT

TRACE

 

 

 

17.5.2 User Exits and Abnormal Termination Exits

This section discusses migration considerations for user and abnormal termination exits, and the similarities and differences between the exits for OS/390 Language Environment and LE/VSE.

17.5.2.1 Assembler User Exits

Three default assembler user exits are provided with LE/VSE. They are:

CEEBXITA (batch)

CEECXITA (CICS)

CEEBX05A (VS COBOL II compatibility)

The default CEEBXITA is linked into the distributed batch initialization/termination phases (CEEBINIT and CEEPIPI); the default CEECXITA is linked into the distributed CICS library support routines phase, CEECCICS.

You can customize these exits to suit your requirements and link them directly to applications for use on an application-specific basis.

OS/390 Language Environment provides default assembler exits with the same names as these, and they also are linked into the batch and CICS initialization and termination load modules, and the CICS support routine load module.

However, these assembler exits may not perform exactly the same functions when invoked in OS/390 Language Environment as in LE/VSE. If you rely on the function of the default assembler exits, you should examine the OS/390 Language Environment versions to ensure they do what you require.

If you have customized your own assembler exits in LE/VSE, you can make the same customization in OS/390 Language Environment.

OS/390 Language Environment also provides a default assembler user exit for TSO, CEEBXITC, which you may find useful.

17.5.2.2 High-Level Language Exits

A sample High-Level Language (HLL) exit is provided in both LE/VSE and OS/390 Language Environment. This is CEEBINT. In both cases, it does nothing except return to the caller.

You can compile as many of your own HLL exits as you wish, in LE/VSE and in OS/390 Language Environment. In OS/390 Language Environment as in LE/VSE, you can write an HLL exit in C, PL/I or Language Environment-conforming Assembler language, but not in COBOL.

Note: You cannot write an HLL exit in C, for use in LE/VSE 1.1.

364VSE to OS/390 Migration Workbook

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IBM OS/390 manual User Exits and Abnormal Termination Exits, Assembler User Exits, High-Level Language Exits, Ceecxita Cics

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.