efn

    OpenVMS usage:ef_number
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Number of the event flag that is set when the service completes.
    If this argument is omitted, event flag 0 is used.

 flags

    OpenVMS usage:mask_longword
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Reserved to VSI. This argument must be zero.

 iosb

    OpenVMS usage:io_status_block
    type:         quadword (unsigned)
    access:       write only
    mechanism:    by reference
    The I/O status block in which the completion status of the
    service is returned as a condition value.

    The outcome of the state change is indicated by the contents of
    the I/O status block.

    To view the I/O status block diagram, see the VSI OpenVMS System
    Services Reference Manual.

 astadr

    OpenVMS usage:ast_procedure
    type:         procedure entry mask
    access:       call without stack unwinding
    mechanism:    by reference
    The AST routine that is executed when the service completes, if
    SS$_NORMAL is returned in R0. The astadr argument is the address
    of the entry mask of this routine. The routine is executed in
    the same access mode as that of the caller of the $TRANS_EVENT
    service.

 astprm

    OpenVMS usage:user_arg
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    The AST parameter passed to the AST routine specified by the
    astadr argument.

 tid

    OpenVMS usage:trans_id
    type:         octaword (unsigned)
    access:       read only
    mechanism:    by reference
    The identifier (TID) of transaction to which the state change is
    to be applied.

 rm_id

    OpenVMS usage:identifier
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    The identifier of the Resource Manager identifier (RMI) with
    which the coordinating Resource Manager (RM) participant is
    associated.

 tx_event

    OpenVMS usage:identifier
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    The operation to be performed on the transaction. For a list of
    the permitted values and the possible successful outcomes, see
    the VSI OpenVMS System Services Reference Manual.