Hardware - zAAP

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For all these models running z/OS there you can add zAAPs, specialized processing units that provide a strategic z/OS Java execution environment. ZAAP stands for zSeries® Application Assist Processor

zAAP was introduced by IBM in 2004.

zAAP has to run under z/OS V1R6 and higher

zAAP runs Java version 1.4.1 and higher

Microcode limits the code execution to Java workloads only

There is a one off fee for a zAAP (around $125,000 at time of writing). IBM mainframe owners do not incur software license charges for zAAPs, reducing their costs of running Java-based applications

All Java applications are switched by z/OS over to the zAPPs which are designed to operate asynchronously with the general CPUs to execute Java programming under control of the IBM Java Virtual Machine (JVM).

The number of zAAPs installed on a mainframe cannot be greater than the number of general CPUs and they require a general CPU to be always available to provide standard services like I/O

Java applications can be migrated to the mainframe with no modifications required

zAAP is a relatively inexpensive option for installations running a large amount of Java work.

Because zAPPs cost significantly less than central processors, and the zAPPs are not included in MSU capacity, Java applications can be off-loaded to a zAPP without any increase in software costs.

zAPPs always run at full speed

zAPPs can only run eligible JAVA code - source applications include: WebSphere Application Server 5.1 (WAS 5.1), CICS/TS 2.3, DB2 Version 7, IMS Version 7 and WebSphere WBI for z/OS

A prerequisite for zAPPs to work is that IBM Software Developers Kit (SDK) for z/OS, Java 2 Technology Edition V1.4 with PFT for APAR PQ86689 must be installed.

More information on zAAP from the IBM site

Clipper Group research document

Detailed look at zAAP by Donald R. Deese

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