With the device type PRINTER or with a blank entry for device type and symbolic device SYSLST (DOS/VS RPG II only)

LRECL is the record length specified in the file description specification plus 1 (for the machine control character)

The first position of each record contains the machine control character. The RECFM in the DCB is the file format specified in the file description with machine control characters. It cannot be overwritten by JCL.

With a blank entry for device type or with a device type other than print or punch device, the RECFM in the DCB is the file format specified in the file description and cannot be overwritten by JCL. Such files can be printed using an IBM utility program, for example, IEBGENER.

4.For print files without line control specifications and without block length specified in the file descriptions:

LRECL is the record length specified in the file description plus 1 (for the machine control character)

RECFM and BLKSIZE must be specified in the JCL.

14.1.3Tape Labels

Whereas in DOS/VS RPG II an exit may be entered on the File Description Specifications form for handling non-standard tape labels, under OS/390 such labels must be handled by a system-wide routine; the entry on the form is ignored. In DOS/VS RPG II, multivolume unlabeled tapes may be specified in the same way. With OS/390, this information is given in JCL statements.

14.1.4 Extent Exit

Exits for DAM files, to check whether the computed track address lies within the extents of the file, are unnecessary under OS/390. Such an extent exit will be ignored.

14.1.5 Processing Options

The options DECK/NODECK, LIST/NOLIST, TERM/NOTERM, and ERRS/NOERRS are conveyed to OS/390 by means of the PARM field in the EXEC statement of the JCL. The default values are DECK, LIST, ERRS, and NOTERM (see OS/VS RPG II Installation Reference, SC33-6122. The other permitted options, NOLINK, CATAL, and LINK, are realized by means of the procedures for compile, for compile and link, or for compile, link, and go.

14.1.6 File Access Methods

The file organizations are supported as in DOS/VS RPG II. The following list correlates the file type and the file processing.

Sequential files are supported as device-independent QSAM files, unless device-dependent features are used. This allows the user to decide at object time where his sequential data items are to reside.

Indexed sequential files are processed with QISAM or BISAM (or both). The OS/390 RPG II compiler chooses the appropriate file access method, according to the entries made on the File Description Specifications form.

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IBM OS/390 manual Tape Labels, Extent Exit, Processing Options, File Access Methods

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.