The PSM$READ_ITEM_DX routine obtains the value of message items
    that are sent by the job controller and stored by the symbiont.
    Use PSM$READ_ITEM_DX to obtain information about the task
    currently being processed, for example, the name of the file
    being printed (SMBMSG$K_FILE_SPECIFICATION) or the name of the
    user who submitted the job (SMBMSG$K_USER_NAME).