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

6947ch02.fm

zSeries Application Assist Processors

The zSeries Application Assist Processor (zAAP) is a PU that is used exclusively for running Java application workloads under z/OS. One CP must be installed with or prior to any zAAP are installed. The number of zAAPs in a machine cannot exceed the number of CPs plus unassigned CPs in that machine. Within the capacity of the sum of all unassigned PUs in up to four books, up to 16 zAAPs can be characterized, depending on the z990 model. Up to 4 zAAPs can be characterized per book. You need an IBM 2084 model D32 with a total of 16 assigned and unassigned CPs to assign 16 zAAPs.

Within the limit of all non-characterized PUs available in the installed configuration, zAAPs can be concurrently added to an existing configuration via Capacity Upgrade on Demand

(CUoD), Customer Initiated Upgrade (CIU), On/Off Capacity on Demand (On/Off CoD), but zAAPs cannot be assigned via CBU.

With On/Off CoD you may concurrently install temporary zAAP capacity by ordering On/Off CoD Active zAAP features up to the number of current zAAPs that are permanently purchased. Also, the total number of On/Off CoD Active zAAPs plus zAAPs cannot exceed the number of On/Off Active CPs plus the number of CPs plus the number unassigned CPs on a z990 server.

For more information about CUoD, CIU or On/Off CoD see Chapter 8, “Capacity upgrades” on page 185. If the installed books have no unassigned PUs left, the assignment of the next zAAP may require the installation of an additional book.

PUs characterized as zAAPs within a configuration are grouped into the ICF/IFL/zAAP processor pool. The ICF/IFL/zAAP processor pool appears on the hardware console as ICF processors. The number of ICFs shown is the sum of IFL, ICF, and zAAP processors on the server.

zAAPs are orderable by feature code (FC 0520). Up to one zAAP can be ordered for each CP or unassigned CP configured in the machine.

Important: The zAAP is a specific example of an assist processor that is known generically as an Integrated Facility for Applications (IFA). The generic term IFA often appears in panels, messages, and other online information relating to the zAAP.

zAAPs and LPAR definitions

zAAP processors can be defined as dedicated or shared processors in a logical partition and are always related to CPs of the same partition. For a logical partition image both CPs and zAAPs logical processors are either dedicated or shared.

Purpose of a zAAP

zAAPs are designed for z/OS Java code execution. When Java code must be executed (i.e under control of Websphere) the z/OS Java Virtual Machine (JVM) calls the function of the zAAP. The z/OS dispatcher then suspends the JVM task on the CP it is running on and dispatches it on an available zAAP. After the Java application code execution is finished the z/OS dispatcher redispatches the JVM task on an available CP after which normal processing is resumed. This reduces the CP time needed to run WebSphere applications, freeing capacity for other workloads.

A zAAP only executes Java Virtual Machine (JVM) code and is the only authorized user of a zAAP in association with some z/OS infrastructural code as the z/OS dispatcher, and supervisor services. A zAAP is not able to process I/O or clock comparator interruptions and does not support operator controls like IPL.

Chapter 2. System structure and design 49

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IBM 990 manual ZSeries Application Assist Processors, ZAAPs and Lpar definitions, Purpose of a zAAP
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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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