9.1.1 Product Installation

The VTAM installation procedures for OS/390 are very different from those for VSE, since this is the area where the operating system differences are most influential. To install OS/390 VTAM you must perform the following steps:

∙Allocate data sets for VTAM. OS/390 VTAM can make use of a large number of data sets, depending on the options selected. In 9.1.1.1, ªVTAM Data Setsº we describe the essential ones; for a complete description (including the optional ones used for APPN, CMIP management and so on) please refer to the VTAM Installation and Migration Guide.

∙Define the channel-attached VTAM devices (37XX, 3174, 3172, channel-to-channel connections and so on) in the OS/390 generation procedure. Alternatively, OS/390 allows these devices to be defined dynamically to its I/O configuration but you must make sure that this is done every time OS/390 is restarted.

∙Determine the CSA and ECSA storage to be used by VTAM, and make appropriate changes to the OS/390 startup definitions. To work out how much storage your VTAM address space will use, go to the Web site at www.ibm.networking.com/vtaprod/vtastor.html where you will find an interactive application that does it for you.

∙Install VTAM from the product tapes using SMP. If you have received VTAM as part of OS/390 or Communications Server/390 this may already have been done. Note that some VTAM modules are linked into the OS/390 nucleus, so a new VTAM installation requires an OS/390 restart. Subsequent updates and fixes may not require a system restart, since most of the VTAM code is now loaded from link and LPA libraries.

∙Create a VTAM start procedure in SYS1.PROCLIB (or another procedure library known to JES). Figure 17 on page 187 shows a sample working procedure that contains all the essential data sets used by VTAM.

∙Copy and modify your VTAM definitions and tables into the new OS/390 libraries.

9.1.1.1 VTAM Data Sets

The data sets that VTAM must have available in order to run are summarized below. They may have any data set names you wish to assign to them, but VTAM recognizes most of them by their data definition (DD) names so that is how we identify them. Figure 17 on page 187 shows a VTAM start procedure that refers to them.

1The VTAM load modules are loaded from SYS1.LINKLIB (or an authorized library concatenated to SYS1.LINKLIB), and from SYS1.LPALIB. These data sets are not specific to VTAM, and do not need to be referenced in the VTAM start procedure. The VTAM initialization module is read from SYS1.LINKLIB and the rest of the VTAM product modules are read into the link pack area from SYS1.LPALIB.

2SISTCLIB contains the VTAM modules which are loaded into CSA and ECSA. This data set is a PDS containing load modules, and must be allocated with DCB=(RECFM=U,BLKSIZE= whatever optimum block size your installation has decided upon). In our procedure we have used the default name of SYS1.SISTCLIB.

3STEPLIB contains those modules which are not part of VTAM, but which VTAM uses to manage the network. Examples might include the NCP loader

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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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