For more information on the benefits of system-managed storage, refer to the following publications:

DFSMS/MVS General Information, GC26-4900

Implementing System-Managed Storage, SC26-3123

DFSMS/MVS Planning for Installation, SC26-4919

RACF General Information, GC23-3723

Getting Started with DFSORT, SC26-4109

5.3.4 Implementing DFSMS

Implementation of DFSMS is not required for OS/390, but many of the newer functions available with OS/390 and DFSMS/MVS require system-managed data and the associated activation of the Storage Management Subsystem (SMS) address space. The following is a small sampling of some of the functions requiring data that is system-managed:

Allocation of OpenEdition Hierarchical File System (HFS) data sets.

Allocation of Extended Format data sets which provides:

VSAM System-Managed-Buffering (SMB)

VSAM Extended Addressability

VSAM Compression

SAM Tailored Compression

Reduction of out-of-space failures

VSAM Record Level Sharing (RLS)

A complete list of new functions available with DFSMS/MVS and considerations for implementing them can be found in DFSMS/MVS Planning for Installation, SC26-4919.

DFSMS implementation can be a phased migration using a milestone approach. The five major milestones are:

1.Enabling the software base

2.Activating the storage management subsystem

3.Managing temporary data

4.Managing permanent data

5.Managing tape data

Using the milestone approach allows you to begin with low-risk implementation activities that establish a base for the staged migration of your data to storage management. In later milestones, your early experience is used to achieve greater data and storage automation. The milestone process is documented in Implementing System-Managed Storage, SC26-3123. Please refer to the publication for more detail.

In conjunction with the milestone approach to implement DFSMS, you can use the DFSMS Fast Implementation Technique (FIT) to plan the implementation. DFSMS FIT uses a question-and-answer approach to create a DFSMS design tailored to your installations needs, and a data classification system that allows you to use your data set naming standards already in place. It helps you quickly identify the different types of data to which you want to assign specific

data-set-level, SMS-management policies.

102VSE to OS/390 Migration Workbook

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IBM OS/390 manual Implementing Dfsms

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.