Upgrading Java runtime so we need to know how does the USS server point to Java runtime.
OPS/MVS
The OPSUSS servers don't use Java by themselves. It can be that you have a rule or REXX program that is running a script that calls a Java program.
The Java path may have been added to the ENVFILE member of the OPSUSS server in case some program requires it:
//ENVFILE DD DISP=SHR,DSN=prefix.CCLXCNTL(USSENV00)