VMS Help System Services, $CREATE GFILE (Alpha Only)  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    On Alpha systems, creates a permanent global disk file section to
    which processes can map.

    This service accepts 64-bit addresses.

    Format

      SYS$CREATE_GFILE  gs_name_64 ,ident_64 ,file_offset_64

                        ,length_64 ,chan ,acmode ,flags

                        ,return_length_64 [,fault_cluster]

    C Prototype

      int sys$create_gfile  (void *gs_nam_64, struct _secid

                            *ident_64, unsigned __int64

                            file_offset_64, unsigned __int64

                            length_64, unsigned short int chan,

                            unsigned int acmode, unsigned int flags,

                            unsigned __int64 *return_length_64,...);

1 - Arguments

 gs_name_64

    OpenVMS usage:section_name
    type:         character-coded text string
    access:       read only
    mechanism:    by 32- or 64-bit descriptor-fixed-length string
                  descriptor
    Name of the global section. The gs_name_64 argument is the 64-
    bit virtual address of a naturally aligned 32- or 64-bit string
    descriptor pointing to this name string.

 ident_64

    OpenVMS usage:section_id
    type:         quadword (unsigned)
    access:       read only
    mechanism:    by 32- or 64-bit reference
    Identification value specifying the version number of a global
    section. The ident_64 argument is a quadword containing three
    fields. The ident_64 argument is the 32- or 64-bit virtual
    address of a naturally aligned quadword that contains the
    identification value.

    The first longword specifies the matching criteria in its low-
    order two bits. The valid values, symbolic names by which they
    can be specified, and their meanings are as follows:

           Symbolic
    Value  Name           Match Criteria

    0      SEC$K_MATALL   Match all versions of the section.
    1      SEC$K_MATEQU   Match only if major and minor
                          identifications match.
    2      SEC$K_MATLEQ   Match if the major identifications are
                          equal and the minor identification of the
                          mapper is less than or equal to the minor
                          identification of the global section.

    If you specify the ident_64 argument as 0, the version number and
    match control fields default to 0.

    The version number is in the second longword and contains
    two fields: a minor identification in the low-order 24 bits
    and a major identification in the high-order 8 bits. You can
    assign values for these fields by installation convention to
    differentiate versions of global sections. If no version number
    is specified when a section is created, processes that specify a
    version number when mapping cannot access the global section.

 file_offset_64

    OpenVMS usage:byte offset
    type:         quadword (unsigned)
    access:       read only
    mechanism:    by value
    Byte offset into the file that marks the beginning of the
    section. The file_offset_64 argument is a quadword containing
    this number. If you do not specify the file_offset_64 argument or
    specify it as 0, the section is created beginning with the first
    byte in the file.

    The file_offset_64 argument must be a multiple of virtual disk
    blocks.

 length_64

    OpenVMS usage:byte count
    type:         quadword (unsigned)
    access:       read only
    mechanism:    by value
    Length, in bytes, of the global disk file section to be created.
    The length specified must be 0 or a multiple of virtual disk
    blocks. If the length specified is 0 or extends beyond end-of-
    file (EOF), the global disk file section is created up to and
    including the virtual block number that contains EOF.

 chan

    OpenVMS usage:longword
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Number of the channel on which the file has been accessed. The
    chan argument is a longword containing this number. The access
    mode at which the channel was opened must be equal to or less
    privileged than the access mode of the caller.

    You can use the OpenVMS Record Management Services (RMS) macro
    $OPEN to access a file; the file options parameter in the file
    access block must indicate a user file open (UFO keyword).

 acmode

    OpenVMS usage:access_mode
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Access mode that is to be the owner of the pages created during
    the mapping. The acmode argument is a longword containing the
    access mode.

    The $PSLDEF macro in STARLET.MLB and the file PSLDEF.H in
    SYS$STARLET_C.TLB define the following symbols and their values
    for the four access modes:

    Value      Symbolic Name      Access Mode

    0          PSL$C_KERNEL       Kernel
    1          PSL$C_EXEC         Executive
    2          PSL$C_SUPER        Supervisor
    3          PSL$C_USER         User

 flags

    OpenVMS usage:mask_longword
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Flag mask specifying the type of global section to be created as
    well as its characteristics. The flags argument is a longword bit
    vector in which each bit corresponds to a flag. The $SECDEF macro
    and the SECDEF.H file define a symbolic name for each flag. You
    construct the flags argument by performing a logical OR operation
    on the symbol names for all desired flags.

    The following table describes each flag that is valid for the
    $CREATE_GFILE service:

    Flag          Description

    SEC$M_CRF     Pages are copy-on-reference. By default, pages are
                  shared.
    SEC$M_DZRO    Pages are demand-zero pages. By default, they are
                  not zeroed when copied.

                  Note that SEC$M_DZRO and SEC$M_CRF cannot both be
                  set and that SEC$M_DZRO set and SEC$M_WRT clear is
                  an invalid combination.
    SEC$M_GBL     Pages form a global section. By default, this flag
                  is always present in this service and cannot be
                  disabled.
    SEC$M_PERM    Global section is permanent. By default, this flag
                  is always present in this service and cannot be
                  disabled.
    SEC$M_SYSGBL  Pages form a system global section. By default,
                  pages form a group global section.
    SEC$M_WRT     Pages form a read/write section. By default, pages
                  form a read-only section.

    All other bits in the flags argument are reserved for future
    use by Compaq and should be specified as 0. The condition value
    SS$_IVSECFLG is returned if any undefined bits are set or if an
    illegal combination of flags is set.

 return_length_64

    OpenVMS usage:byte count
    type:         quadword (unsigned)
    access:       write only
    mechanism:    by 32- or 64-bit reference
    The length of the global section created. The return_length_64
    argument is the 32- or 64-bit virtual address of a naturally
    aligned quadword into which the service returns the length of the
    global section in bytes.

 fault_cluster

    OpenVMS usage:byte count
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Page fault cluster in byte units indicating how many pages are
    to be brought into memory when a page fault occurs for a single
    page. The fault cluster specified is rounded up to a multiple of
    CPU-specific pages.

    If this argument is specified as 0, the system default page fault
    cluster is used. If this argument is specified as more than
    the maximum allowed for the system, no error is returned. The
    systemwide maximum is used.