15.2.2.5 SMESSAGE or LMESSAGE

This option requests the compiler to supply messages in short or long format. This is particularly useful for interactive users using only slow terminals (printers).

15.2.2.6 IMPRECISE

This is used for 360/91 and 360/195 only.

15.2.2.7 INTERRUPT

This option requests that control be given to an ATTENTION type of ON- UNIT in case of attention at the terminal. It is only of interest for conversational programs written to execute under TSO or CMS, or when tuning a batch program written interactively under TSO or CMS when the PL/I CHECKOUT compiler is not available.

15.2.2.8 TERMINAL

This option is used only in an interactive environment. It allows the specification of additional options controlling the display of results at the terminal. The following options can be specified with the option TERM: AGGREGATE ATTRIBUTES ESD INSOURCE LIST MAP OPTIONS SOURCE STORAGE and XREF.

15.2.3 Execution Options

These are not unique to MVS!! For DOS, however, they apply only to CICS/VS transactions!

15.2.3.1 ISASIZE

This option allows control of the management of storage used by PL/I during the execution of the program. By default, PL/I obtains an ISA (Initial Storage Area) of half the available storage after the load module is loaded, unless a user installation established some other default when the PL/I Transient Library was installed. Setting the proper ISASIZE for every projection MVS PL/I program and every DOS/VS PL/I CICS/VS transaction is the most important single thing one can do to optimize PL/I program performance!

15.2.3.2 REPORT

This option allows you to obtain statistics on the memory usage by PL/I during execution of the program. Refer to 15.11, ªStorage Management in PL/Iº on page 345. Use the output of the REPORT option to set ISASIZE correctly. Do not run programs in production with this option turned on. It is expensive.

15.2.3.3 COUNT FLOW

It is possible at execution to suppress the COUNT and FLOW options requested at compilation. This is useful as it is possible to have a program in production, compiled with these options, but turn them off at execution time. If a problem arises, it will then be possible to repeat the execution of the program without having to recompile it. Normally, however, these options are ²compiled out² of production programs, since they add overhead in the executable code.

Chapter 15. PL/I 337

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IBM OS/390 manual Execution Options
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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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