the sample classes trap all errors in this way, this means that the calling programs
do not need to handle any exceptions thrown by the output redirection class. You
can use this method to avoid making changes to your calling programs. Be careful
that you do not send the output redirection class into a loop by attempting to
redirect the error message issued by the class to the destination which has failed.
Using DFHJVMRO to modify the Language Environment enclave for aJVM
DFHJVMRO specifies the run-time options that are used to create the Language
Environment enclave in which a JVM runs. It defines storage allocation parameters
for heap and stack and a number of other options. For CICS, the storage settings
that are supplied in DFHJVMRO are more efficient than the default Language
Environment storage settings. Storage heaps in JVMs, in the Java Applications in
CICS explains how the storage for a JVM is allocated within its Language
Environment enclave.
Youmight want to change the supplied version of the program if you need to:
vUse the RPTO and RPTS options to obtain reports on the storage options set,
and the actual storage used, for JVMs.
vSet storage heap values which are different from the CICS-supplied settings.
Tuning Language Environment enclave storage for JVMsThe CICS Performance
Guide tells you how to use reports obtained using the RPTO and RPTS options
to identify suitable storage heap values.
vAt the request of the IBM service team, set other options to obtain diagnosis
information.
Note that the initial heap size and the heap increment sizes defined by DFHJVMRO
are for minimal values, and less than the minimum heap size for a typical JVM. This
is because the actual amount of storage allocated for the Java heap is controlled by
the Xmx initialization option specified in a JVM profile.
Language Environment run-time options are provided for the JVM by the following
mechanisms, of which you have control over the first two only:
1. The installation-defined defaults generated by the CEEDOPT macro.
2. The DFHJVMRO user-replaceable module.
3. The CICS JVM domain, which enforces certain options.
The DFHJVMRO user-replaceable-module:
vIs invoked during the CEEPIPI preinitialization phase of each Language
Environment enclave that is created for a JVM
vAllows you to alter the default Language Environment run-time options
vMust be written in assembler language
vMust not be translated with the CICS translator
The z/OS V1R7.0 Language Environment Programming Guide, SA22-7561-06, has
complete information about Language Environment run-time options. The options
are specified as character strings, comprising a 2-byte string length followed by the
run-time option. The maximum length allowed for all Language Environment
run-time options is 255 bytes, so you are recommended to use the abbreviated
version of each option, and restrict your changes to a total of under 200 bytes.
670 Customization Guide