acts as an ACB without RESET (add new records to existing file) DISP=OLD overrides IDCAMS REPRO with REUSE

To rewrite a reusable data set - / / DLBL .....,VSAM,DISP=NEW

acts as an ACB with RESET (delete old records, add new records) DISP=NEW overrides IDCAMS REPRO with NOREUSE

Partition Independent File Names

VSE/VSAM partition independent file names start with the character % or characters %%, for example %MY.FILE. These special characters cause the partition identifier (or cpuid and partition identifier) to be appended to the file name when it is DEFINED or accessed. In the example shown, the file name would be MY.FILE.BG if the job was running in the background partition. Access to the file is actually dependent on the partition in which the job is running. Again referring to the example, the same job running in the Foreground 4 partition would access file MY.FILE.F4.

OS/390 does not have partitions. It has address spaces. An address space does not have an external identifier. Address space independence is automatically provided for all temporary data sets.

VSE partition independent files are frequently used for ²temporary² work files. They should be converted to OS/390 temporary data sets. An OS/390 temporary data set is specified by a data set name beginning with the character & or the characters &&. OS/390 supports temporary VSAM data sets only with DFSMS. VSE applications that use permanent partition independent files will require another data set naming convention to operate correctly under OS/390.

VSE/VSAM BACKUP/RESTORE and VSE FASTCOPY

IDCAMS BACKUP/RESTORE is used only for VSE VSAM files, while FASTCOPY is used for non-VSAM and full volume backups. FASTCOPY has a stand-alone component. Equivalent functions are provided in OS/390 via Access Methods Services (EXPORT/IMPORT) for VSAM, DFSMS/MVS utilities (IEBGENER, IEBCOPY and so on) for non-VSAM, and the Data Set Services component of DFSMS (DFSMSdss) for data sets (VSAM and non-VSAM) and full volume dumps. Archive tapes created by VSE/VSAM BACKUP/RESTORE or VSE FASTCOPY cannot be processed by DFSMSdss. Tapes produced by VSE/VSAM EXPORT or REPRO may be processed by OS/390 VSAM. Any non-portable archive tapes should be restored to DASD using the appropriate VSE utilities. Then the DASD files should be dumped to tape using a backup technique compatible with OS/390 backup/restore programs such as DFSMSdss. This needs to be done during the OS/390 migration while both operating systems (VSE and OS/390) are available.

IKQVDU - Volume Cleanup

This VSE/VSAM utility does not exist in OS/390 VSAM. The IKQVDU functions ²SCRATCH DSN² and ²RESET OWNERSHIP² were used to remove unwanted VSE/VSAM data spaces from a volume and to turn off the VSAM ²Ownership Bit²

124VSE to OS/390 Migration Workbook

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IBM OS/390 manual Partition Independent File Names, VSE/VSAM BACKUP/RESTORE and VSE Fastcopy, Ikqvdu Volume Cleanup

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.