∙CATALOG=YES/NO - NO is used if the catalog is to be processed as a normal cluster with normal GET/PUT macros. Programs must be

APF-authorized to process a catalog as a data set.

∙M A C R F = (

-ICI - Improved-Control-Internal-Processing (ICIP) is to be used. ICIP is a VSAM ²fast-path² that reduces CPU utilization. However, the functions

that can be used are severely restricted. See the VSAM Administration Guide for more details.

-CFX - Control blocks and buffers are fixed in real storage. ICI must also be specified.

-DSN - Data Set Name sharing specifies that the basis for sharing control blocks and buffers is by matching VSAM NAMEs when the files are opened by the SAME task. Unless this option is used, a separate ACB that opens the same data set can have the same integrity problems as a program within another region. This includes potential destruction of the file if concurrent updates are allowed. DSN is most commonly used to tie buffers of a base ACB to the control blocks of the base ACB associated with a path.

-SIS - Sequential Insert Strategy is used to override the default control interval or area split algorithm for direct processing. SIS will cause the splits to occur at the insert point rather than at midpoint when direct PUTs are done. Although positioning is lost and writes are done after each direct PUT request, SIS allows more efficient space usage when direct PUTs are done against ascending keys in a KSDS.

-GSR - Global Shared Resources specifies that the data set is to be tied to a common VSAM resource pool of control blocks, strings and buffers that is allocated in the MVS Common System Area (CSA). This provides for VSCR.

-LSR - Local Shared Resources is similar to GSR except the resource pool is built in a single address space and integrity is limited to that region.

∙BSTRNO = n - The number of strings allocated to the base cluster associated with a Path ACB. For a Path ACB, the default is STRNO; however, if you are using DSN sharing to tie a separate base ACB control block

structure to the path, you can specify additional base strings for that purpose. Refer back to ²DSN² for why you want to use DSNAME sharing.

13.2.5.2 EXLST Macro and EXCPAD Routines

A VSE VSAM EXLST macro that has a EXCPAD routine address coded will have to be converted. There is not an equivalent exit routine in MVS VSAM. The closest equivalent is the MVS VSAM UPAD exit routine which allows user processing during a VSAM request. However, the GENCB, MODCB, SHOWCB, and TESTCB macros do not support the UPAD exit routine. Great care should be taken in converting and testing a converted EXCPAD routine, since it is, generally, very complicated code.

13.2.5.3 RPL Macro (Additional MVS Parameters)

∙ECB=address - Request to VSAM to post the specified ECB at the completion of the RPL request.

∙MSGAREA=address - In the case of a physical error, VSAM will place a message in the area address specified.

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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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