∙OS CVOL catalogs - these are a carry-over from the past (pre-OS/390) and are non-VSAM in structure. It has also been announced that OS CVOL catalogs will not be supported after December 31st 1999. For these reasons, they should not be implemented in your OS/390 system.

5.6.2.1 Integrated Catalog Facility (ICF)

The architecture of an ICF catalog is quite different from that of a VSAM catalog. An integrated catalog facility catalog consists of two separate kinds of data sets: a basic catalog structure (BCS) and a VSAM volume data set (VVDS). The BCS can be considered the catalog, whereas the VVDS can be considered an extension of the VTOC.

The BCS is a VSAM key-sequenced data set that contains the following information:

∙VSAM data sets

−volume, security, ownership, and association information

∙Non-VSAM data sets

−volume, ownership, and association information

The VVDS is a VSAM entry-sequenced data set. Its name must be SYS1.VVDS.Vvolser. A VVDS resides on every volume that has VSAM or SMS-managed data cataloged in an ICF catalog. It contains the data set characteristics, extent information, and the volume-related information of the VSAM data sets cataloged in the BCS. For SMS-managed non-VSAM data sets, the VVDS also contains data set characteristics and volume-related information.

If you use a function such as DITTO/ESA′s DID command or the ICKDSF REFORMAT command to change a volume serial number (or volser), only the VOL1 label is changed. Since the REFORMAT command or DID command only changes the volser, it does not change the VVDS name. If a REFORMAT or DID command is used to change the volser, the VVDS name will no longer adhere to the required data set name format of SYS1.VVDS.Vvolser. If the VVDS name does not adhere to the required name format, access to VSAM data sets on that volume has been lost. You won′t be able to RECATALOG these data sets. If your VSE system procedures depend on the use of this capability, those procedures will have to be redesigned.

In the OS/390 environment you should define all your catalogs to be ICF catalogs. ICF catalogs are generally superior in performance, virtual storage savings, recoverability, and space utilization when compared to VSAM catalogs. In addition, many new functions, such as VSAM compression, are only available for SMS managed data sets, which requires use of ICF catalogs. ICF catalogs are not compatible with VSE. You cannot access an ICF catalog from a VSE system.

OS/390 ICF catalogs do not own volumes. Thus, it is possible to have OS/390 VSAM data sets on a given volume that are cataloged in different ICF catalogs. This implies changes to backup and recovery procedures commonly used in VSE/ESA installations.

If a catalog is damaged, restore a backup of the catalog and perform a forward recovery to bring it back into sync. Tools are available for catalog forward recovery such as the Integrated Catalog Facility Recovery Utility (ICFRU). If a cluster is damaged, the old version can be deleted, uncataloged, restored from a backup and then forward recovery can be used to make the cluster data current.

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IBM OS/390 manual Integrated Catalog Facility ICF
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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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