15.6.3 PLICANC

Another possibility offered in the MVS PL/I optimizer is the ability to annul a request for an automatic restart. The function PLICANC provides this service.

In checkpoint-restart MVS PL/I offers more facilities than DOS PL/I. The conversion of PL/I programs poses few syntax problems. On the other hand, to take advantage of automatic restart, some additional work will be necessary in the logic of the program.

15.7 DUMP in PL/I Optimizer

15.7.1 Output File

The PL/I optimizer possesses its own dump routines. They present a number of advantages over the dumps provided by the operating system. Among others, they trace the PL/I control blocks (TCA, DSA and so on). In MVS PL/I optimizer, the dump is edited on a particular file whose DDNAME is PLIDUMP. In DOS this dump is produced on SYSLST. It is therefore necessary to provide a //PLIDUMP

DDcontrol statement in the JCL. If this is absent, the dump is not produced and a message is produced by MVS indicating that

²FILE PLIDUMP COULD NOT BE OPENED - DDNAME MISSING² .

Note that the PLIDUMP file is also used for data requested by the COUNT and REPORT options. Do not suppress the storage report produced by the REPORT option by omitting the PLIDUMP DD card; use NOREPORT to suppress this report.

15.7.2 Options Specific to DOS

The option D (and ND), which asks for information on the opened files and on the modules associated with them, does not exist in MVS. Only the option F (and NF) exists. In practice this trace of called modules is necessary in DOS, because the loading of modules from the TRANSIENT LIBRARY is done by PL/I, which implies that only PL/I knows which modules are loaded. In MVS, the load list keeps track of loaded modules and the option PLIDUMP (TRACE) produces a list of these modules.

The options 48 and 60 request the PL/I dump routines to use different translation tables; there is no equivalent in MVS.

The option R (and NR), which in DOS allows the collection of data on the management of storage, is not required in MVS while calling DUMP, but is replaced by the execution option REPORT (and NOREPORT).

The option Q does not exist and has no equivalent in MVS. In DOS it allows a more succinct dump, consisting of a DOS PDUMP of all of PL/I′s storage. It is used when the 10K or so of storage needed by normal PL/I DUMP is not available.

Chapter 15. PL/I 343

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IBM OS/390 manual Plicanc, Dump in PL/I Optimizer Output File, Options Specific to DOS
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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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