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

6947ch06.fm

CP Logical Processor

WebSphere

EXECUTE JAVA Code

JVM

Call to zAAP

z/OS Dispatcher

Suspend JVM task on z/OSCP logical processor

z/OS Dispatcher

Dispatch JVM task on z/OS CP logical processor

JVM

WebSphere

Figure 6-3 Logical flow of Java code execution on a zAAP

zAAP Logical Processor

JVM

JAVA Application Code

Executing on a zAAP

Processor

JVM

Switch to CP Logical Processor

Figure 6-3 shows the logical flow of Java code running on a z990 server that has a zAAPs available. The Java Virtual Machine (JVM), when it starts execution of a Java program, passes control to the z/OS dispatcher that will verify the availability of a zAAP:

￿If a zAAP is available (not busy), the dispatcher will suspend the JVM task on the CP, and assign the Java task to the zAAP. When the task returns control to the JVM, it passes control back to the dispatcher that will reassign the JVM code execution to a CP.

￿If there is no zAAP available at that time the z/OS dispatcher may allow, a Java task to run on a standard CP (depending on the option used in the OPT statement in the IEAOPTxx member of SYS1.PARMLIB).

zAAPs do not affect the overall MSU or capacity rating of a system or logical partition. That is, adding zAAPs to a system or defining to a logical partition does not affect the software license charges. There is no additional z/OS charge for zAAPs.

Subsystems that exploit zAAPs are:

￿WebSphere Application Server (WAS) V5.1.

￿CICS/TS V2.3.

￿DB2 V8.

￿IMS V8.

￿WebSphere WBI for z/OS.

The functioning of a zAAP is transparent to all IBM and ISV Java programming on JVM 1.4.1 and above.

Three execution options for Java code execution are available. These options are user specified in IEAOPTxx and can be dynamically altered by the SET OPT command.

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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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