arg_vector

    OpenVMS usage:vector
    type:         vector_longword_unsigned
    access:       modify
    mechanism:    by reference
    Vector containing callbacks and login information.

 context

    OpenVMS usage:context
    type:         longword (unsigned)
    access:       modify
    mechanism:    by reference
    Pointer to site's local context.

 user_cond_value

    OpenVMS usage:cond_value
    type:         longword_unsigned
    access:       read only
    mechanism:    by value
    SS$_NORMAL for successful login; otherwise, reason for failure.