15.4.1Not Supported in MVS

15.4.1.1MEDIUM

Physical and logical unit type. This option is ignored by the MVS compiler. The error severity is 8 and gives correct execution. In MVS PL/I the name of the DD statement (DDname) is the name of the file as specified in the DCL. If some other name must be used, it can be supplied via the TITLE option on the OPEN statement.

15.4.1.2 FUNCTION

This option defines the type of operation to be carried out on a 3525, 2560 or 5425. It is ignored in MVS. The error severity is 8 and gives correct execution. If the function exists in MVS, it will be specified in the sub-parameter FUNC of the DCB parameter of the DD statement.

15.4.1.3 ASSOCIATE

This option corresponds to the multiple functions on the 3525. The functions required will be specified in the JCL by the sub-parameters FUNC and AFF of the DCB parameter in the DD statement.

Note: The use of this parameter in MVS PL/I causes an error of severity 12 (serious). Use of this option prohibits the use of spooling.

15.4.1.4 RCE (Read Column Eliminate)

This option is specified in the DCB by the parameter MODE=ER or MODE=CR. A statement FORMAT (nl,n2),(n3,n4) must precede the data in the input stream. Use of this option prohibits the use of spooling.

15.4.1.5 OMR (Optical Mark Read)

This option disappears and re-appears in the DCB: MODE= EO or MODE=CO. It is used for reading optical marks on the 3525, and prohibits the use of spooling.

15.4.1.6 COLBIN

This option is suppressed in MVS PL/I and the equivalent function is supplied to MVS by the sub-parameter MODE=C in the DCB.

15.4.1.7 STACKER

This option is withdrawn from the MVS compiler and supplied by using ASA or machine control characters: CTLASA or CTL360 in PL/I, or equally well RECFM=FBA or RECFM=FBM in the DCB.

15.4.1.8 CMDCHN WTRPROT FILESEC NOFEED VOLSEQ

Options for handling 3540 diskettes, which are not supported by MVS PL/I.

15.4.1.9 UNLOAD

This option does not exist in MVS. The unloading of tapes after a CLOSE is determined by the DISP= parameter of the DD statement.

Chapter 15. PL/I 339

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IBM OS/390 manual Not Supported in MVS
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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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