Supported but to be Avoided, ²TOTAL² Option

15.4.1.10 NOTAPEMK NOLABEL

These are specified in the JCL in the LABEL parameter of the DD statement.

15.4.2 Supported but to be Avoided

In OS most of the environment parameters can be specified in the DCB. At OPEN, MVS merges the information from the program, from the label if the file exists already, and from the DCB parameters in the DD statement. It is therefore damaging to specify the physical blocksize in the program, because a

re-compilation is involved if the blocking factor is to be changed. The following options should therefore be omitted:

BLKSIZE

KEYLENGTH

KEYLOC

15.4.3 The ²TOTAL² Option

A new option can be specified: TOTAL. This option, which is effective only with CONSECUTIVE files, allows PL/I to branch directly to MVS access method routines without using the TRANSIENT library modules; there is therefore a performance improvement. This requires that the file be declared as completely as possible. Only the blocking factor may be specified in the DD statement, and no options may be specified at OPEN. Users must weigh the benefits of improved performance (via the TOTAL option) against the advantages of complete MVS DCB merge.

15.4.4 The SIS Option (Sequential Insert Strategy)

This option applies to (and only to) processing of a VSAM KSDS using a PL/I file with the DIRECT attribute. It causes VSAM to insert new records using SIS (Sequential Insert Strategy) rather than direct insert strategy. All other environment options, in the case of VSAM files, are identical in MVS PL/I and DOS PL/I.

15.5 Calling SORT from PL/I

15.5.1 Interfaces Offered

The DOS PL/I Optimizer provides, through PLISRTx, an interface to DOS/VS

SORT/MERGE Version 2 (5746-SM2) and other VSE supported sorts.

The MVS PL/I Optimizer offers, through an interface of the same name, access to DFSORT (5740-SM1).

The four sort entry points offered by PL/I are the same in MVS and VSE: PLISRTA, PLISRTB, PLISRTC and PLISRTD. The only exits supported by PL/I are E15 and E35.

15.5.2 Parameters to be Passed

The parameters for calling sort are fortunately the same. The number of these parameters depends on the entry point used. Let us take the most general case (PLISRTD) which invokes exits E15 and E35. The parameters to be passed are described in the following sections.

340VSE to OS/390 Migration Workbook

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.

IBM OS/390 Supported but to be Avoided, ²TOTAL² Option, SIS Option Sequential Insert Strategy

Models: OS/390