Migration for Java applications that run in a JVM

Start of changeCICS® Transaction Server for z/OS Version 3 Release 1 supports the JVM provided by the IBM Software Developer Kit for z/OS, Java 2 Technology Edition, Version 1.4.2, which features the persistent reusable JVM technology.

Note:
There are two versions of the IBM Software Developer Kit for z/OS, Java 2 Technology Edition, Version 1.4.2, a 31-bit and a 64-bit version. CICS Transaction Server for z/OS Version 3 Release 1 supports only the 31-bit version, which must be at the 1.4.2 level.
End of change

CICS Transaction Server for z/OS®, Version 2 Release 2 supported the JVM provided by the IBM® Developer Kit for OS/390® Java™ 2 Technology Edition Version 1.3.1s, which also featured the persistent reusable JVM technology. Java programs that ran under CICS Transaction Server for z/OS, Version 2 Release 2 and CICS Transaction Server for z/OS, Version 2 Release 3 can also run under CICS Transaction Server for z/OS Version 3 Release 1.

However, the older type of JVM that was introduced in CICS Transaction Server for OS/390, Version 1 Release 3, which was not reusable, is no longer supported. Any Java programs that ran under CICS Transaction Server for OS/390, Version 1 Release 3 must be migrated to Java 2 to run under the reusable JVM. Application migration issues are discussed at:

http://java.sun.com/j2se/1.4/compatibility.html
http://java.sun.com/products/jdk/1.3/compatibility.html#incompatibilities1.3
and
http://java.sun.com/products/jdk/1.2/compatibility.html

Support for the JVM provided by the IBM Software Developer Kit for z/OS, Java 2 Technology Edition, Version 1.4.2 completely replaces the JVM support provided in CICS TS 1.3. However, you can modify a JVM to run as a single-use JVM and not attempt serial reuse. A single-use JVM is initialized, is used to run a single Java program, and then is automatically destroyed without attempting a JVM reset. You can modify a JVM to be a single-use JVM by specifying either REUSE=NO, or the older option Xresettable=NO, in the JVM profile. The single-use JVM is like the earlier JVM that was supported by CICS in CICS TS 1.3. New Java applications should not be developed in such a way that they can only run in a single-use JVM.

To avoid problems with deprecated APIs, you should develop all new Java programs for CICS Transaction Server for z/OS Version 3 Release 1 using an application development environment that supports Java 2 at the same version of Java as used by CICS. You may run code compiled with an older version of Java in a new runtime, provided that it does not use APIs that have been removed in the newer version of Java.

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