A START APPC,SUB=MSTR,APPC=xx command or a SET APPC=xx command was issued to specify an APPCPMxx parmlib member that activates a logical unit (LU) in the Advanced Program-to-Program Communication (APPC) configuration. However, the system could not open the Virtual Telecommunications Access Method (VTAM®) access method control block (ACB) for the specified LU. This LU is in pending state. Some of the return codes returned from OPEN can be a temporary condition which gets resolved. For example, this message may be encountered when APPC/MVS is activated, but VTAM is not active or completely initialized. To determine if the problem has been resolved, check the status of the LU by issuing the DISPLAY APPC,LU,ALL command. If the LU is now active then the condition has been resolved and no further actions are required.