Only the main thread of an application can access the REXX variable pool. Applications may create and use new threads, but only the original thread that called RexxStart can use RexxVariablePool.
OS/2 EXE modules called from a REXX procedure execute in a new process. Because the modules are not using the same process and thread as the REXX procedure, the modules cannot use RexxVariablePool to access REXX variables. You can use RexxVariablePool from subcommand handlers, external functions and exit handlers.