As it is desirable from both performance and integrity perspectives to separate user data sets into several user catalogs, it is critical that data set names be defined with the above information in mind. If, for example, all data set names begin with CUSTOMER as the first node, then all the data sets will be defined in only one user catalog. If the high order node for some data sets is PAYROLL, and for others INVENTRY, then these data sets could be split between two user catalogs if desired.

It is strongly recommended that data set naming conventions be defined carefully and that they be enforced through training and review procedures during conversion and after the system has been placed into production.

As data set naming conventions can greatly simplify the operation of your OS/390 system, and can also make the migration process simpler, we have included a separate chapter on recommendations for data set naming. See the chapter, 25.4, ªSet Up Standards, Procedures, and Documentationº on page 407, for more information.

5.3 Storage and Space Management

5.3.1 VSE Considerations

Standard VSE system facilities provide for user management of DASD space resources, or for VSAM management of DASD space for SAM files. Many VSE users have OEM vendor disk space management packages, and/or tape library management packages. User management requires manual procedures to maintain catalogs of disk space in use or available, as well as tape volumes in use, and the relationships between tape files and tape volumes. VSE users who have not automated some or all of these functions find manual procedures error prone and slow.

5.3.2 OS/390 Considerations

OS/390′s Direct Access Device Storage Manager (DADSM) and Data Facility -- System Managed Storage (DFSMS) components provide all the capabilities of the VSE system, plus OEM vendor enhancements.

5.3.3 System Managed Storage

System-managed storage is the OS/390 automated approach to managing your system′s storage resources. It uses software programs to manage data security, placement, migration, backup, recall, recovery, and deletion to ensure that current data is available when needed, and obsolete data is removed from storage. The combination of system-managed storage and related hardware and software products is called the DFSMS environment.

With DFSMS, you tailor the system-managed storage environment to your needs. You define the requirements for performance, security, and availability, along with storage management policies used to automatically manage the direct access, tape, and optical devices used by the OS/390 operating systems. The Interactive Storage Management Facility (ISMF), a component of DFSMSdfp, provides the user interface for defining and maintaining these policies and the Storage Management Subsystem (SMS) governs these policies for the system. In this environment, RACF and DFSORT compliment the functions of the base operating system. The following are brief descriptions of the DFSMS/MVS

100VSE to OS/390 Migration Workbook

Page 123 Page 125
Page 124
Image 124
IBM OS/390 manual Storage and Space Management VSE Considerations, System Managed Storage
Page 123 Page 125

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.
Top Page Image Contents