new vendor package that runs under AIX. As guests of VM/ESA, all three can run efficiently while sharing one processor.

You have production applications that need to be reworked to comply with Year 2000. With VM/ESAs Guest Support you can bring up a duplicate of

your production system, set the clock to a date and time beyond the year 2000 then perform test and application debugging without disrupting your current production system.

You have production applications that need to be reworked to comply with changes required by the European Common Currency. With VM/ESAs Guest

Support you can bring up a duplicate of your production system, set the specific elements that affect currency and/or exchange rates, then perform test and application debugging without disrupting your current production system.

If you are considering using Parallel Sysplex. VM/ESA supports guest coupling simulation on the IBM 9672 Parallel Enterprise Servers Generation 3 and Generation 4 and on the IBM Multiprise 2000 Servers (at the appropriate engineering change levels). VM/ESA Guest Coupling Simulation provides for the simulation of one or more complete parallel sysplexes within a single VM/ESA system image. The intent is to provide a pre-production testing platform for a coupled-system installation. Other than the processors required, there is no special hardware needed: no coupling links and no external coupling facilities. All guest operating systems coupled within a simulated sysplex can only be coupled (through simulated coupling links) to coupling facilities also running as guests of the same VM/ESA system. Up to 32 virtual machines can be coupled within a simulated sysplex, with each such virtual machine coupled to up to eight coupling facility virtual machines.

Performance Benefits

Guest systems may see performance improvements by exploiting VM/ESA features. For example, both virtual disk in storage and minidisk cache allow guests to avoid real I/Os by using data in storage and caching techniques.

Reduced Hardware and Migration Cost

Guest systems such as OS/390, MVS, TPF, VSE, VM and others can share devices such as channels, printers, and DASD, which VM/ESA efficiently manages. VM/ESA adds value to such devices merely by the way it manages them. A good example is VM/ESAs minidisk support, which allows one real disk to function as if it were several smaller disks (such as multiple IPL-able minidisks). VM/ESA also simulates some hardware devices (such as unit record devices and CTC adapters).

For migrating to a new release from an older VM, VSE, MVS, OS/390, or TPF, VM/ESA gives you the ability to bring up the new system on the same physical processor saving you the cost of a separate processor or LPAR hardware. This new system can share the devices and resources of your existing VM/ESA system thus eliminating the cost of separate hardware for new system migration testing. When testing is complete switching over to your new production system is only a matter of configuration/table changes and can be accomplished in minutes. These technical and cost saving advantages provided by VM/ESA and VMs Guest Support are fundamental requirements upon which the VM/ESA product was built and have been carefully refined over the years. This gives

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IBM OS/390 manual Performance Benefits, Reduced Hardware and Migration Cost

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.