Unlike Java 8, IBM Semeru Runtime Certified Edition for z/OS 11 and newer are available in 64-bit addressing-mode only. Pure Java code is addressing-mode agnostic and will run on either 31-bit or 64-bit Java SDKs. However, your application may contain native non-Java 31-bit portions invoked via Java Native Interface (JNI) that require porting to 64-bit, in order to run with the latest Semeru SDKs. While the porting of native code to 64-bit requires some effort, here are some references to help you embark on the journey:

General principles and considerations to port applications to 64-bit

This will be the most performant and scalable option, as your native code can take advantage of the above-the-bar virtual storage, along with streamlined 64-bit XPLINK linkages.

• Java perspective - https://www.ibm.com/docs/en/sdk-java-technology/8?topic=applications-porting-java-64-bit-systems

• Language Environment perspective - https://community.ibm.com/community/user/ibmz-and-linuxone/blogs/nai-jie-li/2022/03/16/get-above-the-bar-zos-language-environment-64-bit?communityKey=e7b7d299-8509-4572-8cf1-c1112684644f

Support for 31-bit native library interoperability with 64-bit SDK for Java

This feature allows 31-bit single-threaded applications to still invoke 64-bit Java code, and is useful for the scenarios where existing native code has dependencies on 31-bit only interfaces and/or require more effort to port to 64-bit.

• Java perspective: https://www.ibm.com/docs/en/semeru-runtime-ce-z/17?topic=wja-using-31-bit-native-c-c-code-64-bit-java-vm

• COBOL perspective: https://community.ibm.com/community/user/ibmz-and-linuxone/blogs/nicole-trudeau1/2021/10/14/mixed-amode-31-64-cobol-programs?communityKey=dc94cb0f-7361-47d9-854f-dfcbdbbf04a3

• IMS perspective: https://community.ibm.com/community/user/ibmz-and-linuxone/blogs/carlos-alvarado1/2022/02/16/31-bit-cobol-can-now-talk-to-64-bit-java?communityKey=eba3ada3-db89-4dca-9154-328195f5e560

Middleware considerations

Various middleware products manage the Java runtime environment, and can be optionally configured to use 64-bit SDK for Java.

• Db2 Store Procedures: https://www.ibm.com/docs/en/db2-for-zos/13?topic=jspudf-moving-from-31-bit-java-routines-64-bit-java-routines

• IMS workloads: https://www.ibm.com/docs/en/ims/15.5.0?topic=tm-jvm-64-bit-support-migration-considerations