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A few months ago there was a short discussion about CRTJVAPGM, whether
or not it is version dependent, and how to use the JDKVER parameter. I
ran across this today and wanted to pass it along.
http://publib.boulder.ibm.com/infocenter/iseries/v5r4/topic/rzaha/rzaha.pdf
System i Programming
IBM Developer Kit for Java
Version 5 Release 4
P.38:
For best performance at optimization level 40, it is recommended to
preform CRTJVAPGM on each i5/OS release or JDK version change. This is
especially true if the JDKVER facility is used on CRTJVAPGM, as
this results in methods from the Sun JDK being inlined into your JVAPGM.
This can be a great advantage to performance. If, however, changes are
made in the JDK on subsequent releases that invalidate those inlines,
the programs may actually run slower than at lower optimizations. This
is because special case code must be run to get proper operation.
I also noticed this on P.17:
In previous releases of the IBM Developer Kit for Java, you had to
recreate a Java program if you changed the JAR file or ZIP file in any
way, because the attached Java program would become unusable. This is no
longer true. In many cases, if you change a JAR file or ZIP file, the
Java program is still valid and you do not have to recreate it. If
partial changes are made, such as when a single class file is updated
within a JAR file, you only need to recreate the affected class files
that are within the JAR file.
- --
Pete Hall
pete@xxxxxxxxxxxxxx
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