On Alpha and Integrity server 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$M_WRT Pages form a read/write section. By default, pages
form a read-only section.
All other bits in the flags argument are reserved for future
use by VSI and should be specified as 0. The condition value
SS$_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.