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

Java application code can either run on a CP or an zAAP. The user can manage the use of CPs such that Java application code runs only on a CP, only on an zAAP, or on both when zAAPs are busy.

For the logical flow of a Java code execution on a zAAP, see Figure 6-3 on page 139.

Software support

zAAPs do not change the software model number of the z990 server. IBM software product license charges based on the software model number are not affected by the addition of zAAPs.

z/OS Version 1.6 is a prerequisite for supporting zAAPs, together with IBM SDK for z/OS, Java 2 Technology Edition V1.4.1.

Exploiters of zAAPs include:

￿WebsSphere Application Server 5.1 (WAS 5.1)

￿CICS/TS 2.3

￿DB2 Version 8

￿IMS Version 8

￿WebSphere WBI for z/OS

System Assist Processors

A System Assist Processor (SAP) is a PU that runs the Channel Subsystem Licensed Internal Code to control I/O operations.

All SAPs perform I/O operations for all logical partitions. All z990 models have standard SAPs configured. The IBM 2084 model A08 has two SAPs; the model B16 has four SAPs; the model C24 has six SAPs; the model D32 has eight SAPs as the standard configuration.

Channel cards are assigned across SAPs to balance SAP utilization and improve I/O subsystem performance.

A standard SAP configuration provides a very well-balanced system for most environments. However, there are application environments with very high I/O rates (typically some TPF environments). In this case, optional additional SAPs can be ordered. Assignment of additional SAPs can increase the capability of the Channel Subsystem to perform I/O operations.

In z990 servers, the number of SAPs can be greater than the number of CPs and the number of used STIs.

Optional additional orderable SAPs

An option available on all models is additional orderable SAPs. These additional SAPs increase the capacity of the Channel Subsystem to perform I/O operations, usually suggested for TPF environments. The maximum number of optional additional orderable SAPs depends on the model and the number of available uncharacterized PUs in the configuration:

￿IBM 2084-A08: maximum additional orderable SAPs is 2

￿IBM 2084-B16: maximum additional orderable SAPs is 4

￿IBM 2084-C24: maximum additional orderable SAPs is 6

￿IBM 2084-D32: maximum additional orderable SAPs is 8

50IBM eServer zSeries 990 Technical Guide

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IBM 990 manual System Assist Processors, Software support, Optional additional orderable SAPs
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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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