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

6947ch02.fm

Remember that logical partitions are currently limited to a maximum size of 128 GB of storage.

2.2.11 LPAR Dynamic Storage Reconfiguration (DSR)

Dynamic Storage Reconfiguration (DSR) on z990 servers allows an operating system running in a logical partition to add non-disruptively its reserved storage amount to its configuration, if any unused storage exists. This unused storage can be obtained when another logical partition releases some storage, or when a concurrent memory upgrade takes place.

With enhanced DSR, the unused storage does not have to be continuous.

When an operating system running in a logical partition assigns a storage increment to its configuration, PR/SM will check if there are any free storage increments and will dynamically bring the storage online.

PR/SM will dynamically take offline a storage increment and will make it available to other partitions when an operating system running in a logical partition releases a storage increment.

2.2.12 I/O subsystem

All models have one I/O subsystem. The I/O subsystem should be considered as the physical entity that encompasses all control functions and all connections to all devices.

The z990 I/O subsystem provides great flexibility and high availability and performance, allowing:

￿High bandwidth

The z990 I/O subsystem can handle up to 96 GB/sec; this is four times the z900 server’s bandwidth. Individual channels can have up to 2 Gb/sec data rates.

￿Wide connectivity

A z990 server can be connected to an extensive range of interfaces, using protocols such as Fibre Channel Protocol (FCP) for Small Computer System Interface (SCSI), Gigabit Ethernet (GbE), Fast Ethernet (FENET), 1000Base-T Ethernet, and High Speed Token Ring, along with FICON, ESCON, and coupling link channels.

￿Concurrent channel upgrades

It is possible to concurrently add channels to a z990 server provided there are unused channel positions in an I/O cage. Additional I/O cages can be previously installed on an initial configuration via Plan Ahead, to provide greater capacity for concurrent upgrades. This capability may help eliminate an outage to upgrade the channel configuration. For more information about concurrent channel upgrades, see “CUoD for I/O” on page 193.

￿Dynamic I/O reconfiguration

Dynamic I/O reconfiguration enhances system availability by supporting the dynamic addition, removal, or modification of channel paths, control units, I/O devices, and I/O configuration definitions to both hardware and software (if it has this support), without requiring a planned outage.

￿ESCON port sparing and upgrading

The ESCON 16-port I/O card includes one unused port dedicated for sparing in the event of a port failure on that card. Other unused ports are available for growth of ESCON channels without requiring new hardware, enabling concurrent upgrades via Licensed Internal Code.

Chapter 2. System structure and design 71

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IBM 990 manual Lpar Dynamic Storage Reconfiguration DSR, 12 I/O subsystem
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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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