6947ch06.fm Draft Document for Review April 7, 2004 6:15 pm
140 IBM eServer zSeries 990 Technical Guide

Option 1: Java dispatching by priority (honor_priority=yes)

Option 1 is the default option and specifies that standard CPs execute both Java and
non-Java work in priority order when zAAPs are not configured. When zAAPs are configured
they only execute Java work in priority order while the CPs execute normal tasks and JVM
tasks in priority order. This option is oriented towards servicing work with the highest priority
first, regardless of the type of work.

Option 2: Java discretionary crossover (crossover=yes)

Standard CPs execute Java work in priority order only if no non-Java (standard) work is
available to be dispatched. This way Java work may execute on a CP as if it has a lower
priority than the non-Java work. This option is oriented towards environments where not
enough zAAP capacity is available and the Java work has no need for priority over non-Java
work. When executed on a zAAP, Java work is handled in priority order.

Option 3: No Java crossover (crossover=no)

This option is set to prevent Java work to be executed on a CP. If for example Sub Capacity
Workload License Charging is applicable, Java work that is executed on a CP will increase
CP utilization and consequently may increase the software charges for non-Java work. Also,
is ample zAAP capacity is available this option assures that all Java work is done on a zAAP.
Only if the last available zAAP would fail, crossover to a standard CP is enforced.
6.2.3 HCD support
HCD support for both Compatibility support, and Exploitation support allows the definition of
the z990 processor and I/O configuration from an existing system. If the z990 processor is
part of a S/390 microprocessor cluster, the HCD support also allows the IOCDS to be written
directly from an existing system. The new HCD elements apply to z/VM and z/OS.
HCD uses a concept: the validated work IODF. This is a new status for an IODF data set. It
contains a complete set of validated processor, LCSS, partition, channel, control unit, and I/O
device definitions. A validated work IODF would not normally contain the physical channel
identifiers (PCHIDs) for channels.
Closely allied with this function, support is added to allow HCD to work with the z990 CHPID
Mapping Tool (CMT) to assign PCHIDs. This support allows an IOCP source statement data
set to be created from a validated work IODF; it also allows the data from the CHPID Mapping
Tool to be merged with the validated work IODF to complete the PCHID assignments.
Compatibility support for HCD allows an installation to do the following:
򐂰Define a z990 environment with multiple Logical Channel Subsystems
򐂰Make dynamic hardware changes to LCSS 0 only. Devices cannot be added, modified or
deleted if they are also defined to another LCSS. This requires a Power-on Reset.
Exploitation Support for HCD has full dynamic change support for all LCSSs.
6.2.4 Automation changes
Several commands and messages have been adapted to accommodate the two-digit LPAR
identifier.
6.2.5 SMF support
CPU and PR/SM activity data is recorded by RMF in the SMF type 70 subtype 1 records.
Prior to the z990, these records were always shorter than 32 KB. With the increased number