The data set names of the user catalogs are contained in the OS/390 master catalog. Information necessary to locate the user catalogs is also defined in the master catalog. The high-level-qualifiers of data sets that are to be cataloged in each user catalog are also identified in the OS/390 master catalog.

OS/390 data set names are divided into qualifiers. The data set name consists of up to 44 characters, grouped into qualifiers of up to eight characters each, separated by periods. For example ²DEPT1.PAYROLL.YTD.DATA² contains four qualifiers. The high-level qualifier consists of the characters before the first period in the data set name. It is also known as the catalog ²ALIAS² name, because it determines which user catalog OS/390 will search to find the data set information. Thus the master catalog normally has many ALIAS name ²pointers² to multiple user catalogs. An OS/390 user catalog may have many ALIAS names associated with it. Each TSO user name will be associated with a particular user catalog through an alias which must be defined for it.

The following diagram illustrates the master catalog to user catalog structure relationship.

 

 

￿￿￿￿￿￿￿￿￿￿￿￿￿

DEPT4 &

DEPT1 & JONES

￿

OS/390

￿

PAYROLL

 

￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿

Master

￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿

 

￿

￿

Catalog ￿

￿

 

￿

￿￿￿￿￿￿￿￿￿￿￿￿￿

￿

 

￿

DEPT2 ￿

￿ DEPT3

￿

 

￿

 

￿

￿

 

￿

 

￿

 

￿

￿

 

￿

￿￿￿￿￿￿￿￿￿￿￿

￿￿￿￿￿￿￿￿￿￿￿

￿￿￿￿￿￿￿￿￿￿￿

￿￿￿￿￿￿￿￿￿￿￿

￿

User ￿

￿ User

￿

￿

User ￿

￿ User ￿

￿ Catalog ￿

￿ Catalog ￿

￿ Catalog ￿

￿ Catalog ￿

￿￿￿￿￿￿￿￿￿￿￿

￿￿￿￿￿￿￿￿￿￿￿

￿￿￿￿￿￿￿￿￿￿￿

￿￿￿￿￿￿￿￿￿￿￿

DEPT1.DATA

DEPT2.DATA

DEPT3.JUNK

DEPT4.DATA

DEPT1.CUST

DEPT2.STATS

 

 

PAYROLL.CURR

DEPT1.STORES

 

 

 

 

PAYROLL.YTD

JONES.TSET.DATA

 

 

 

 

 

 

 

 

Figure 9.

OS/390 Master and User Catalog Structure

 

The system searches for data sets by finding, via the master catalog, in which user catalog the data set is cataloged. For example, for a data set named DEPT1.PAYROLL.YTD.DATA, the master catalog would direct OS/390 catalog management to the appropriate user catalog (identified by the DEPT1 ALIAS name), and the data set information would then be retrieved from this user catalog. The manual, Managing Catalogs, SC26-4914 contains more details about the use of catalogs. It discusses aliases, catalog search order and so on, in Chapter 2.

116VSE to OS/390 Migration Workbook

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IBM OS/390 manual DEPT1 & Jones, DEPT2 DEPT3, DEPT1.DATA, DEPT3.JUNK DEPT4.DATA DEPT1.CUST, Payroll.Curr
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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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