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
    Flags specifying options for the service. The flags argument is
    a longword bit mask in which each bit corresponds to an option
    flag. The $DDTMDEF macro defines symbolic names for these option
    flags, which are defined in $END_TRANS Option Flags.

    All undefined bits must be 0. If this argument is omitted, no
    flag is set.

    Table SYS-15 $END_TRANS Option Flags

    Flag           Description

    DDTM$M_SYNC    Set this flag to specify that successful
                   synchronous completion is to be indicated by
                   returning SS$_SYNCH. When SS$_SYNCH is returned,
                   the asynchronous system trap (AST) routine is not
                   called, the event flag is not set, and the I/O
                   status block is not filled in.
    DDTM$M_        Indicates that the service should return to the
    NOWAIT         caller without waiting for final cleanup. Note
                   that $END_TRANSW with the DDTM$M_NOWAIT flag set
                   is not equivalent to $END_TRANS. The former does
                   not return until the operation has been initiated,
                   while $END_TRANS returns when the operation has
                   been queued.

                   The full range of status values may be returned
                   from a nowait call.

 iosb

    OpenVMS usage:io_status_block
    type:         quadword (unsigned)
    access:       write only
    mechanism:    by reference
    I/O status block in which the following information is returned
    contains:

    o  The completion status of the service. This is returned as a
       condition value.

    o  The outcome of the transaction. If the service returns SS$_
       NORMAL, the outcome of the transaction is commit. If the
       service returns SS$_ABORT, the outcome of the transaction
       is abort.

    o  An abort reason code that gives one reason why the transaction
       aborted, if the completion status of the service is SS$_ABORT.

    The $DDTMMSGDEF macro defines symbolic names for these abort
    reason codes, which are described in Abort Reason Codes:

    Table SYS-16 Abort Reason Codes

    Symbolic Name        Description

    DDTM$_ABORTED        The application aborted the transaction.
    DDTM$_COMM_FAIL      A communications link failed.
    DDTM$_INTEGRITY      A resource manager integrity constraint
                         check failed.
    DDTM$_LOG_FAIL       A write operation to the transaction log
                         failed.
    DDTM$_ORPHAN_        Unauthorized branch caused failure.
    BRANCH
    DDTM$_PART_SERIAL    A resource manager serialization check
                         failed.
    DDTM$_PART_TIMEOUT   The timeout specified by a resource manager
                         expired.
    DDTM$_SEG_FAIL       A process or image terminated.
    DDTM$_               A DECdtm transaction manager serialization
    SERIALIZATION        check failed.
    DDTM$_SYNC_FAIL      The transaction was not globally
                         synchronized (an authorized branch had not
                         been added).
    DDTM$_TIMEOUT        The timeout specified on $START_TRANS
                         expired.
    DDTM$_UNKNOWN        The reason is unknown.
    DDTM$_VETOED         A resource manager was unable to commit the
                         transaction.

    Refer to the HP OpenVMS System Services Reference Manual to view
    the structure of the I/O status block.

 astadr

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

 astprm

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

 tid

    OpenVMS usage:trans_id
    type:         octaword (unsigned)
    access:       read only
    mechanism:    by reference
    Identifier (TID) of the transaction to be ended.

    If this argument is omitted, $END_TRANS ends the default
    transaction of the calling process.