If your installation lets SMP/E default to that directory, then the same set up you use for Java stored procedures in DB2 for z/OS V8 will continue to work. But if you change that, then you need to set a new ENVAR in your JAVAENV dataset such as "DB2_BASE=/usr/lpp/db9a/db2910_base" so we can find our code. Otherwise, you'll see this error when the WLM-SPAS tries to start up: java.lang.NoClassDefFoundError: com.ibm.db2.dsnx9.JARLoader
I know, there are an awful lot of "moving parts" to setting up for running java stored routines. You need the DB2 universal java driver, the z/OS JVM, and JCL and a JAVAENV dataset. The stored procedures redbook has a good chapter on setup. It's a complex environment, but a very powerful one, too!