AS/400 Flags Disclosure
-----------------------

Q:  What is QPRCMLTTSK?

A:  Documentation from Work Management, document SC41-5340.

2.3.84 QPRCMLTTSK System Value

QPRCMLTTSK is processor multi-tasking.  This system value allows you to
turn on and turn off the processor multi-tasking capability.  If
enabled, more than one set of task data will be resident in each CPU.
Some work load may experience increased performance due to caching
implications.  The possible values for processor multi-tasking are:

     '0': Processor multi-tasking is turned off. 
     '1': Processor multi-tasking is turned on. 

Q:  How are memory pools adjusted?  

A:  Many of our systems come with large amounts of memory.  The memory
can be allocated to different pools, and then subsystems can be defined
to use a specific memory pool when running.  For the SPECjbb runs, our
tests were run in the *MACHINE and *BASE pools, and the excess memory
was moved to alternate pools.   This was done to show that the test
could run in a smaller amount of memory than the actual amount of system
memory.  Using the WRKSYSSTS command, you can see how much memory has
been allocated to each pool, and interactively update the amount in each
pool.

Detailed description of adjusting memory pools can be found in the Work
Management documentation, SC41-5340, section 4.2 Storage Pools.

Q:  Describe the AS/400 Java Transformer

A:  The following documentation comes from the AS/400 Developer Kit for
Java publication
 
Java transformer

The Java transformer is an IBM Operating System/400 (OS/400) component
that preprocesses class files to prepare them to run using the AS/400
Java virtual machine.  The Java transformer creates an optimized program
object that is persistent and is associated with the class file.  In the
default case, the program object contains a compiled, 64-bit RISC
machine instruction version of the class.  The Java interpreter does not
interpret the optimized program object at runtime.  Instead, it directly
runs when the class file is loaded.

You do not need to do anything to start the Java transformer.  It runs
automatically the first time that the class file runs on the system,
unless you explicitly request that the class file run in interpreted
mode.

You can use the Create Java Program (CRTJVAPGM) command to explicitly
start the Java transformer.  The CRTJVAPGM command optimizes the class
file or JAR file while the command runs, so nothing needs to be done
while the program is running.  This improves the speed of the program
the first time that it runs.  Using the CRTJVAPGM command, instead of
relying on default optimization, ensures the best optimization possible
and also better utilizes space for the Java programs that are associated
with the class file or JAR file.

Using the CRTJVAPGM command on a class file, JAR file, or ZIP file
causes all the classes in the file to be optimized, and the resulting
Java program object will be persistent.  This results in better runtime
performance.  You can also change the optimization level or select an
optimization level other than the default of 10 by using the CRTJVAPGM
command or the Change Java Program (CHGJVAPGM) command.  At optimization
level 40, interclass binding is performed between the classes within a
JAR file, and in some cases, the classes are inlined.  Interclass
binding improves the call speed.  Inlining removes the call entirely.
In some cases, you can inline methods between classes within the JAR
file or ZIP file.  Specifying OPTIMIZE(*INTERPRET) on the CRTJVAPGM
command causes any classes that are specified on the command to be
verified and prepared to run in interpreted mode.  The Run Java (RUNJVA)
command can also specify OPTIMIZE(*INTERPRET).  This parameter specifies
that any classes running under the Java virtual machine are interpreted,
regardless of the optimization level of the associated program object.
This is useful when debugging a class that was transformed with an
optimization level of 40.
   To force interpretation, use INTERPRET(*YES).

Q:  Why do we use -opt40 on the java command line?

A:  According to the SPECjbb run rules, the jbb_no_precompile.jar file
cannot be precompiled prior to running the java command.  This flag
indicates that any class/jar/zip which has not been precompiled (i.e.,
does not currently have an attached java program) should be implicitly
created for direct execution by the Java transformer at optimization
level 40 during the run.

Q:  How do you prevent precompilation of the classes in
jbb_no_precompile.jar?

A:  Once a class/jar/zip file has been compiled for direct execution,
either explicitly or implicitly, there is a java program associated with
that file that is used for subsequent direct execution runs.  The
DLTJVAPGM command is used to "delete" or "detach" the java program that
was previously created.  This was done prior to each SPECjbb run.

Q:  Why do we set the os400.class.path.system property to POST on the
JDK 1.1.8 run?

A:  In 1.1.8 on the AS/400, by default the user classpath is appended
after the system classpath.  When running SPECjbb, there is a validity
check to determine if jbb.jar is the first entry in the current
classpath.  Without this property, our 1.1.8 run would be invalid, since
the entries from the system classpath appear before jbb.jar.