VMS Help  —  System Services, $ENQ  Arguments
 efn

    OpenVMS usage:ef_number
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Number of the event flag to be set when the request has been
    granted or canceled. Cancellation occurs if you use $DEQ with the
    cancel modifier or if the waiting request is chosen to break a
    deadlock. The efn argument is a longword containing this number;
    however, $ENQ uses only the low-order byte.

    Upon request initiation, $ENQ clears the specified event flag
    (or event flag 0 if efn was not specified). Then, when the lock
    request is granted, the specified event flag (or event flag 0)
    is set unless you specified the LCK$M_SYNCSTS flag in the flags
    argument.

 lkmode

    OpenVMS usage:longword_unsigned
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Lock mode requested. The lkmode argument is a longword specifying
    this lock mode.

    Each lock mode has a symbolic name. The $LCKDEF macro defines
    these symbolic names. The following table gives the symbolic name
    and description for each lock mode:

    Lock Mode     Description

    LCK$K_NLMODE  Null mode. This mode grants no access to the
                  resource but serves as a placeholder and indicator
                  of future interest in the resource. The null mode
                  does not inhibit locking at other lock modes;
                  further, it prevents the deletion of the resource
                  and lock value block, which would otherwise occur
                  if the locks held at the other lock modes were
                  dequeued.

    LCK$K_CRMODE  Concurrent read. This mode grants the caller read
                  access to the resource while permitting write
                  access to the resource by other users. This mode is
                  used to read data from a resource in an unprotected
                  manner, because other users can modify that data as
                  it is being read. This mode is typically used when
                  additional locking is being performed at a finer
                  granularity with sublocks.

    LCK$K_CWMODE  Concurrent write. This mode grants the caller
                  write access to the resource while permitting write
                  access to the resource by other users. This mode is
                  used to write data to a resource in an unprotected
                  fashion, because other users can simultaneously
                  write data to the resource. This mode is typically
                  used when additional locking is being performed at
                  a finer granularity with sublocks.

    LCK$K_PRMODE  Protected read. This mode grants the caller read
                  access to the resource while permitting only read
                  access to the resource by other users. Write access
                  is not allowed. This is the traditional share lock.

    LCK$K_PWMODE  Protected write. This mode grants the caller write
                  access to the resource while permitting only read
                  access to the resource by other users; the other
                  users must have specified concurrent read mode
                  access. No other writers are allowed access to the
                  resource. This is the traditional update lock.

    LCK$K_EXMODE  Exclusive. The exclusive mode grants the caller
                  write access to the resource and allows no access
                  to the resource by other users. This is the
                  traditional exclusive lock.

    The following table shows the compatibility of lock modes:

    Table SYS-17 Compatibility of Lock Modes

    Mode of                Mode of Currently Granted Locks

    Requested

    Lock       NL    CR    CW    PR     PW    EX

    NL         Yes   Yes   Yes   Yes    Yes   Yes
    CR         Yes   Yes   Yes   Yes    Yes   No
    CW         Yes   Yes   Yes   No     No    No
    PR         Yes   Yes   No    Yes    No    No
    PW         Yes   Yes   No    No     No    No
    EX         Yes   No    No    No     No    No
    __________________________________________________________________
    Key to Lock Modes:

     NL-Null
     CR-Concurrent read
     CW-Concurrent write
     PR-Protected read
     PW-Protected write
     EX-Exclusive

 lksb

    OpenVMS usage:lock_status_block
    type:         longword (unsigned)
    access:       write only
    mechanism:    by 32- or 64-bit reference
    Lock status block in which $ENQ writes the final completion
    status of the operation. The lksb argument is the 32- or 64-bit
    address of the 8-byte lock status block.

    The lock status block can optionally contain a 16-byte or a 64-
    byte lock value block. The initial value of the lock value block
    is zero (0).

    o  When you specify the LCK$M_VALBLK flag in the flags argument,
       the lock status block contains a lock value block. In this
       case, the 16-byte lock value block appears at the beginning
       of the first byte following the eighth byte of the lock status
       block, bringing the total length of the lock status block to
       24 bytes.

    o  When you specify the LCK$M_XVALBLK flag together with the
       LCK$M_VALBLK flag in the flags argument, the lock status
       block contains an extended lock value block. In this case,
       the 64-byte lock value block appears at the beginning of
       the first byte following the eighth byte of the lock status
       block, bringing the total length of the lock status block to
       72 bytes.

       The LCK$M_XVALBLK flag is valid only on Alpha and Integrity
       server systems.

    To view the lock status block format diagram and status block
    fields table, see the HP OpenVMS System Services Reference
    Manual.

 flags

    OpenVMS usage:mask_longword
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Flags specifying options for the $ENQ operation. The flags
    argument is a longword bit mask that is the logical OR of each
    bit set, where each bit corresponds to an option.

    The $LCKDEF macro defines a symbolic name for each flag bit.

    To view the table describing each flag, see the HP OpenVMS System
    Services Reference Manual.

 resnam

    OpenVMS usage:char_string
    type:         character-coded text string
    access:       read only
    mechanism:    by 32- or 64-bit descriptor-fixed-length string
                  descriptor
    Name of the resource to be locked by this lock. The resnam
    argument is the 32- or 64-bit address of a character string
    descriptor pointing to this name. The name string can be from
    1 to 31 bytes in length.

    If you are creating a new lock, the resnam argument should be
    specified because the default value for the resnam argument
    produces an error when it is used to create a lock. The resnam
    argument is ignored for lock conversions.

 parid

    OpenVMS usage:lock_id
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Lock identification of the parent lock. The parid argument is a
    longword containing this identification value.

    If you do not specify this argument or specify it as 0, $ENQ
    assumes that the lock does not have a parent lock. This argument
    is optional for new locks and is ignored for lock conversions.

 astadr

    OpenVMS usage:ast_procedure
    type:         procedure value
    access:       call without stack unwinding
    mechanism:    by 32- or 64-bit reference
    AST service routine to be executed when the lock is either
    granted or converted. The astadr argument is the 32- or 64-bit
    address of this routine. The AST is also delivered when the lock
    or conversion request is canceled. Cancellation occurs if you use
    $DEQ with the cancel modifier or if the waiting request is chosen
    to break a deadlock.

    If you specify the astadr argument, the AST routine executes at
    the same access mode as the caller of $ENQ.

 astprm

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

 blkast

    OpenVMS usage:ast_procedure
    type:         procedure value
    access:       call without stack unwinding
    mechanism:    by 32- or 64-bit reference
    Blocking AST routine to be called whenever this lock is granted
    and is blocking any other lock requests. The blkast argument
    is the 32- or 64-bit address of this routine. Locks that are
    converting to a new mode, but that are not yet granted in the new
    mode, do not receive blocking ASTs.

    You can pass a parameter to this routine by using the astprm
    argument.

 acmode

    OpenVMS usage:access_mode
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Access mode to be associated with the resource name. The acmode
    argument indicates the least privileged access mode from which
    locks can be queued on the resource.

    This argument does not affect the access mode associated with the
    lock or its blocking and completion ASTs. The acmode argument is
    a longword containing the access mode. The $PSLDEF macro defines
    the following symbols for the four access modes:

    Symbol        Access Mode

    PSL$C_KERNEL  Kernel
    PSL$C_EXEC    Executive
    PSL$C_SUPER   Supervisor
    PSL$C_USER    User

    The $ENQ service associates an access mode with the lock in the
    following way:

    o  If you specified a parent lock (with the parid argument),
       $ENQ uses the access mode associated with the parent lock and
       ignores both the acmode argument and the caller's access mode.

    o  If the lock has no parent lock (you did not specify the parid
       argument or specified it as 0), $ENQ uses the least privileged
       of the caller's access mode and the access mode specified
       by the acmode argument. If you do not specify the acmode
       argument, $ENQ uses the caller's access mode.

 rsdm_id

    OpenVMS usage:longword
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Resource domain identification. The rsdm_id argument is a
    longword specifying the resource domain association through
    which a new lock is to be taken. This argument is ignored for
    lock conversions and sublocks (parid is nonzero). Valid resource
    domain identifiers are returned from the $SET_RESOURCE_DOMAIN
    service, or by the constants RSDM$K_SYSTEM_RSDM_ID or RSDM$K_
    PROCESS_RSDM_ID, which are defined by the $RSDMDEF macro in
    STARLET.

 nullarg

    OpenVMS usage:null_arg
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Placeholding argument reserved by HP.
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