IBM 990 - Manual (Page 150)

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zSeries 990 Technical Guide
Planned z/OS V1.6 support
Exploitation Support (and Compatibility Support) is integrated into the base of z/OS V1.6
(planned to be available in September 2004). Some unique support offered by this release is:
Dynamic addition and deletion of a logical partition name
24 processors (sum of CPs and zAAPs) within a single logical partition
zSeries Application Assist Processors (zAAPs)
Dynamic addition and deletion of a logical partition name
z/OS V1.6 supports dynamic naming of a reserved logical partition. Reserved logical
partitions are defined with a name placeholder ‘
* ’ and can be dynamically named or
removed from the list of named logical partitions.
A dynamic partition must be reserved in the IOCDS and will be established when a Power-On
Reset with this IOCDS is executed. A reserved partition has a MIF ID and usage type
assigned.
24 processors within a single logical partition
z/OS V1.6 supports up to 24 processors (the sum of CPs and zAAPs). Note that the sum of
initial and reserved processors, including CPs and zAAPs, for an ESA/390 mode logical
partition can go up to 32 processors.
zSeries Application Assist Processor (zAAP)
Support for the zSeries Application Assist Processor is introduced in z/OS V1.6. This z/OS
release is planned to be available in September 2004.
A zAAP reduces the standard processor (CP) capacity requirements for Java applications
freeing up capacity for other workload requirements. zAAPs do not increase the MSU value of
the processor and therefore do not affect the software license fee.
zAAPs only run Java code. The IBM SDK for z/OS Java 2 Technology Edition (the Java Virtual
Machine), in cooperation with z/OS and PR/SM, directs JVM processing from CPs to zAAPs.
Apart from the cost savings this may realize, the integration of Java based applications with
their associated data base systems such as DB2, IMS, or CICS®, may simplify the
infrastructure, for example, reducing the number of TCP/IP programming stacks and server
interconnect links. Furthermore, processing latencies that would occur if Java application
servers and their data base servers were deployed on separate server platforms are
prevented.
Figure 6-3 on page 139 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).
Note: zAAPs are not supported for a z/OS guest under z/VM.