/sys$common/syshlp/helplib.hlb RMS, $READ, Arguments  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 rab

    OpenVMS usage:rab
    type:         longword (unsigned)
    access:       modify
    mechanism:    by reference

    RAB control block whose contents are to be used as indirect
    arguments for the Read service call. The rab argument is the
    address of the RAB control block.

 err

    OpenVMS usage:ast_procedure
    type:         procedure value
    access:       call without stack unwinding
    mechanism:    by reference

    AST-level error completion routine that the service invokes if
    the operation is unsuccessful. The err argument is the address of
    the entry mask of this user-written completion routine.

 suc

    OpenVMS usage:ast_procedure
    type:         procedure value
    access:       call without stack unwinding
    mechanism:    by reference

    AST-level success completion routine that the service invokes if
    the operation is successful. The suc argument is the address of
    the entry mask of this user-written completion routine.