6947ch07.fm

Draft Document for Review April 7, 2004 6:15 pm

Value of CPU management

The benefits of CPU management include the following:

￿Logical CPs perform at the fastest uniprocessor speed available.

This results in the number of logical CPs tuned to the number of physical CPs of service being delivered by the logical partition current weight. If the logical partition is getting 4 equivalent physical CPs of service and has 8 logical CPs online to z/OS, then each logical CP only gets half of an equivalent physical CP. For example, if a CP delivers 200 MIPS, half of it will deliver 100 MIPS. This occurs because each logical CP gets fewer time slices.

￿Reduced PR/SM overhead.

There is a PR/SM overhead for managing a logical CP. The higher the number of logical CPs in relation to the number of equivalent physical CPs, the higher the PR/SM overhead. This is because PR/SM has to do more processing to manage the number of logical CPs that exceeds the number of equivalent physical CPs.

￿z/OS gets more control over how CP resources are distributed.

Using CPU management, z/OS is able to manage CP resources in relation to WLM goals for work. This was not possible in the past when a logical partition had CP resources assigned and used these as best it could in one logical partition. Now, z/OS is able to change the assigned CP resources (LPAR weights) and place them where they are required for the work. CPU management does the following:

–Identifies what changes are needed and when.

–Projects the likely results on both the work it is trying to help and the work that it will be taking the resources from.

–Performs the changes.

–Analyzes the results to ensure the changes have been effective.

There is also the question of the speed at which an operator can perform these actions. WLM can perform these actions every Policy Adjustment interval, which is normally ten seconds as determined by WLM. It is not possible for an operator to perform all the tasks in this time.

For additional information on implementing LPAR CPU management under IRD see the redbook: z/OS Intelligent Resource Director, SG24-5952.

7.5.2 Dynamic Channel Path Management

There is no such thing as a “typical” workload.The requirements for processor capacity, I/O capacity, and other resources vary throughout the day, week, month, and year.

Dynamic Channel Path Management (DCM) provides the ability to have the system automatically manage the number of paths available to disk subsystems. By making additional paths available where they are needed, the effectiveness of your installed channels is increased, and the number of channels required to deliver a given level of service is potentially reduced.

DCM also provides availability benefits by attempting to ensure that the paths it adds to a control unit have as few points of failure in common with existing paths as possible, and configuration management benefits by allowing the installation to define a less specific configuration. On a z990 where paths can be shared by Multiple Image Facility (MIF), DCM will coordinate its activities across logical partitions within a single Logical Channel Subsystem on a server within a single sysplex.

178IBM eServer zSeries 990 Technical Guide

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IBM 990 manual Dynamic Channel Path Management, Value of CPU management
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990 specifications

The IBM 990 series, often referred to in the context of IBM's pioneering efforts in the realm of mainframe computing, represents a unique chapter in the history of information technology. Introduced in the late 1960s, the IBM 990 series was designed as a powerful tool for enterprise-level data processing and scientific calculations, showcasing the company's commitment to advancing computing capabilities.

One of the main features of the IBM 990 was its architecture, which was built to support a wide range of applications, from business processing to complex scientific computations. The system employed a 32-bit word length, which was advanced for its time, allowing for more flexible and efficient data handling. CPUs in the IBM 990 series supported multiple instructions per cycle, which contributed significantly to the overall efficiency and processing power of the machines.

The technology behind the IBM 990 was also notable for its use of solid-state technology. This provided a shift away from vacuum tube systems that were prevalent in earlier computing systems, enhancing the reliability and longevity of the hardware. The IBM 990 series utilized core memory, which was faster and more reliable than the magnetic drum memory systems that had been standard up to that point.

Another defining characteristic of the IBM 990 was its extensibility. Organizations could configure the machine to suit their specific needs by adding memory, storage, and peripheral devices as required. This modular approach facilitated the growth of systems alongside the technological and operational demands of the business environments they served.

In terms of software, the IBM 990 series was compatible with a variety of operating systems and programming environments, including FORTRAN and COBOL, enabling users to access a broader array of applications. This versatility was a significant advantage, making the IBM 990 an appealing choice for educational institutions, research facilities, and enterprises alike.

Moreover, the IBM 990 was engineered to support multiprocessing, which allowed multiple processes to run simultaneously, further increasing its effectiveness in tackling complex computing tasks.

In summary, the IBM 990 series represents a significant advancement in computing technology during the late 20th century. With a robust architecture, versatile configuration options, and a focus on solid-state technology, the IBM 990 facilitated substantial improvements in data processing capabilities, making it a cornerstone for many businesses and academic institutions of its time. Its impact can still be seen today in the continued evolution of mainframe computing.
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