It occurs because the SYSVIEW API modules are not available in the environment where the OPS/REXX program is executing.
Resolution
The SYSVIEW load library must be accessible via LNKLST or STEPLIB in the environment where the OPS/REXX program is executing. For example, if the program is executing under a OPSOSF server the SYSVIEW library must be added to the STEPLIB concatenation of the OSF server or to LNKLST.