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

6947ch07.fm

Where several channels are attached from a z990 LCSS to a switch, they can be considered a resource pool for accessing any of the control units attached to the same switch. To achieve this without DCM would require deactivating paths, performing a dynamic I/O reconfiguration, and activating new paths. DCM achieves the equivalent process automatically, using those same mechanisms.

Channels managed by DCM are referred to here as “managed” channels. Channels not managed by DCM are referred to as “static” channels.

Workload Manager dynamically moves channel paths through the ESCON Director from one I/O control unit to another in response to changes in the workload requirements. By defining a number of channel paths as managed, they become eligible for this dynamic assignment.

By moving more bandwidth to the important work that needs it, your disk I/O resources are used much more efficiently. This may decrease the number of channel paths you need in the first place, and could improve availability because, in the event of a hardware failure, another channel could be dynamically moved over to handle the work requests.

Dynamic Channel Path Management runs on a zSeries server in z/Architecture mode, in both basic and LPAR mode. The participating z/OS system images can be defined as XCFLOCAL, MONOPLEX, or MULTISYSTEM.

If a system image running Dynamic Channel Path Management in LPAR mode is defined as being part of a multisystem sysplex, it also requires a CF level 9 Coupling Facility structure, even if it is the only image currently running on the system.

Dynamic Channel Path Management operates in two modes:

￿Balance mode

In balance mode, DCM will attempt to equalize performance across all of the managed control units.

￿Goal mode

In goal mode, which is available only when WLM is operating in goal mode on systems in an LPAR cluster, DCM will still attempt to equalize performance, as in balance mode. In addition, when work is failing to meet its performance goals due to I/O delays, DCM will take additional steps to manage the channel bandwidth accordingly, so that important work meets its goals.

Enabling Dynamic Channel Path Management involves defining managed channels and control units via HCD. On the Hardware Management Console, you then need to ensure that all of the appropriate logical partitions are authorized to control the I/O configuration.

For additional information on implementing Dynamic Channel Path Management under IRD see z/OS Intelligent Resource Director, SG24-5952.

Value of Dynamic Channel Path Management

Dynamic Channel Path Management provides the following benefits:

￿Improved overall image performance

Improved image performance is achieved by automatic path balancing (WLM compatibility and goal mode) and Service Policy (WLM goal mode).

￿Maximum utilization of installed hardware

Channels will be automatically balanced, providing opportunities to use fewer I/O paths to service the same workload.

Chapter 7. Sysplex functions 179

Page 192 Page 194
Page 193
Image 193
IBM 990 manual Value of Dynamic Channel Path Management
Page 192 Page 194

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.
Top Page Image Contents