Do not use JOBCAT or STEPCAT statements in OS/390

In predecessors of today¢s OS/390 systems, it was not uncommon to use JCL

DDstatements specifying user catalogs to be used for a job or a step (JOBCAT or STEPCAT). This procedure was obsoleted with the advent of the Integrated Catalog Facility and its ALIAS mechanism, and it should not be used.

The OS/390 JOBCAT and STEPCAT DD statements when used in jobstreams, bypass the normal catalog search technique via the ALIAS. Their use can cause incorrect cataloging of duplicate ²new² data sets. In addition, these statements are not supported by Data Facility Systems Managed Storage (DFSMS). JOBCAT and STEPCAT should not be used when migrating to OS/390.

5.6.4 OS/390 - VSE/VSAM Catalog Compatibility

Note

Even though (non-concurrent) sharing of VSAM between VSE and OS/390 is described below, it is recommended that this practice not be extended past the migration period. As VSAM changes are probable with new releases of OS/390 DFP or VSE/VSAM, ²flip flopping² of data sets and catalogs between VSE and OS/390 should be limited to the migration period.

Note that VSAM catalog dates are stored with a two-digit year representation. Although VSE/VSAM has been updated to interpret these dates using sliding window technologies, DFP/VSAM has not been changed similarly. DFP/VSAM use of VSAM catalogs will not function correctly after December 31st 1999.

See the WSC flash article Figure 8 on page 113.

A VSE/VSAM master or user catalog can be designed (DEFINEd) to be compatible and therefore accessible by an OS/390 system. Only VSAM user catalogs may be ported between environments. For a VSE/VSAM catalog to be compatible (and used in an OS/390 system), the catalog has to have the following characteristics:

1.The catalog was defined with the IMBED option.

This is the VSE/VSAM default, but many users specify NOIMBED for space savings within the catalog itself.

2.The catalog is on a device supported by OS/390.

Generally, the disk devices not supported by OS/390 are FBA Direct Access Storage Devices.

Note that non-VSAM data sets within VSAM data spaces, such as

VSE/VSAM-managed SAM files, cannot be accessed in OS/390.

Chapter 5. Disk and Tape Storage Considerations 117

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IBM manual 4 OS/390 VSE/VSAM Catalog Compatibility, Do not use Jobcat or Stepcat statements in OS/390

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.