clientPID

    OpenVMS usage:process_ID
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference
    Address of a longword containing the External Process
    Identification (EPID) of the client process for which the server
    is reserving the slot.

 persona

    OpenVMS usage:persona
    type:         longword (unsigned)
    access:       write only
    mechanism:    by reference
    Address of a longword into which the persona identification
    is written. This service sets aside the identification for the
    client's to-be-delegated persona.