HP OpenVMS Systems Documentation

Shared page tables are always created for Galaxy-wide shared sections of at least 128 pages.

Shared page tables consume the same internal OpenVMS data structures as global sections. The system parameters GBLPAGES and GBLSECTIONS must account for the additional global pages and the additional global section.

Note that only one set of shared page tables can be associated with any memory-resident or Galaxy-wide section. By default, shared page tables will allow write access. To create shared page tables that allow only read access, you must set the READ_ONLY_SHPT flag. A process that requires write access to a section where the shared page tables only allow read access must use private page tables to map the section.

To use the shared page tables associated with a memory-resident global section, a process must first create a shared page table region (with $CREATE_REGION_64). Additionally, a subsequent request to map to the memory-resident global section must do the following:

• Specify a shared page table region to the mapping request (see Table SYS-22 for additional information).
• Specify the same access mode as specified by the acmode argument to this service.
• Set the flag SEC$M_WRT in the mapping request only if shared page tables allow write access.
• Set the flag SEC$M_EXPREG in the mapping request or provide a CPU-specific page table page aligned virtual address. (See the description of the CREATE_REGION_64 service for information about calculating virtual addresses that are aligned to a CPU-specific page table page boundary.)

If a shared page table region is not specified, process-private page tables are used to map to the global section.

If the service returns an error status value that is neither SS$_INSFLPGS nor SS$_MRES_PFNSMALL, a value is not returned in the reserved_length_64 argument.

If the service returns a successful condition value or if SS$_INSFLPGS or SS$_MRES_PFNSMALL is returned and the reserved_length_64 argument is specified as a nonzero address, the length in bytes of the global section as registered in the Reserved Memory Registry is returned in the reserved_length_64 argument.

To map a Galaxy shared section or a memory resident section, see the $CRMPSC_GDZRO_64 service.

For additional information, see the HP OpenVMS Alpha Partitioning and Galaxy Guide.

Required Privileges

To create a permanent memory-resident global DZRO section, the process must have the following privileges or rights identifiers:

• SYSGBL privilege to create a system global section (if flag SEC$M_SYSGBL is set)
• PRMGBL privilege to create a permanent global section
• VMS$MEM_RESIDENT_USER rights identifier to create a memory-resident section
• SHMEM privilege on OpenVMS Galaxy systems to create an object in Galaxy shared memory.

Required Quota

None

Related Services

$CRMPSC_GDZRO_64, $DGBLSC, $MGBLSC_64

Condition Values Returned

SS$_NORMAL	A Galaxy-wide section already existed and has been made available.
SS$_CREATED	Global section has been created.
SS$_CREATED_SHPT	Global section has been created with shared page tables.
SS$_ACCVIO	The gs_name_64 descriptor cannot be read by the caller, or the reserved_length_64 argument was specified as a nonzero value and cannot be written by the caller.
SS$_BADRAD	The specified RAD contains no memory, or if the specified RAD is greater than or equal to the maximum number of RADs on the system.
SS$_DUPLNAM	A global section of the same name already exists; a new global section was not created.
SS$_GPTFULL	There is no more room in the system global page table to set up page table entries for the global section or for the shared page tables.
SS$_GSDFULL	There is no more room in the system space allocated to maintain control information for global sections.
SS$_INSFLPGS	Insufficient fluid pages available.
SS$_INSFRPGS	Insufficient free shared pages or private pages.
SS$_INV_SHMEM	Shared memory is not valid.
SS$_IVLOGNAM	The specified global section name has a length of 0 or has more than 43 characters.
SS$_IVPROTECT	The protection argument format is invalid.
SS$_IVSECFLG	An invalid flag, a reserved flag, or an invalid combination of flags was specified.
SS$_IVSECIDCTL	The match control field of the global section identification is invalid.
SS$_LEN_NOTPAGMULT	The length_64 argument is not a multiple of CPU-specific pages.
SS$_LOCK_TIMEOUT	An OpenVMS Galaxy lock timed out.
SS$_MRES_PFNSMALL	Preallocated, contiguous, aligned physical memory specified in the Reserved Memory Registry is smaller than the length specified for the global section by the length_64 argument.
SS$_NOBREAK	An OpenVMS Galaxy lock is held by another node and was not broken.
SS$_NOMEMRESID	The process attempted to create a memory-resident section but was not holding the correct identifier (VMS$MEM_RESIDENT_USER).
SS$_NOPRMGBL	The process does not have the privileges to create or delete a permanent group global section (PRMGBL).
SS$_NOSYSGBL	The process does not have the privileges to create or delete a system global section (SYSGBL).
SS$_SECTBLFUL	There are no entries available in the system global section table for the global section or for the shared page tables.
SS$_TOOMANYLNAM	The logical name translation of the gs_name_64 argument exceeded the allowed depth of 10.

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,...);

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:

Value	Symbolic 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 HP 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.

Description

The Create Permanent Global Disk File Section service allows a process to create a permanent global disk file section.

Creating a global disk file section involves defining all or part of a disk file as a section. The global section is created as entire pages; however, the last page in the section might correspond to less than a full page of virtual disk blocks. Only the number of virtual disk blocks specified by the length_64 argument, or as many as exist in the disk file, will be associated with the disk file section.

Upon successful completion of this service, the return_length_64 argument will contain the length of the global section created in even multiples of virtual disk blocks.

The security profile of the file is used to determine access to the global section. For a global disk file section to allow write access to the file during the mapping of the global section, the channel used to open the file must allow write access to the file.

Required Privileges

To create a global section, the process must have the following privileges:

• SYSGBL privilege to create a system global section (if flag SEC$M_SYSGBL is set)
• PRMGBL privilege to create a permanent global section

Required Quota

None

Related Services

$CRMPSC, $CRMPSC_GFILE_64, $DGBLSC, $MGBLSC, $MGBLSC_64

Condition Values Returned

SS$_CREATED	The service completed successfully. The specified global section did not previously exist and has been created.
SS$_ACCVIO	The gs_name_64 argument or the return_length_64 argument cannot be read by the caller.
SS$_CHANVIO	The specified channel was assigned from a more privileged access mode.
SS$_DUPLNAM	A global section of the same name already exists; a new global section was not created.
SS$_ENDOFFILE	The file_offset_64 argument specified is beyond the logical end-of-file.
SS$_EXBYTLM	Process has exceeded the byte count quota; the system was unable to map the requested file.
SS$_GPTFULL	There is no more room in the system global page table to set up page table entries for the section.
SS$_GSDFULL	There is no more room in the system space allocated to maintain control information for global sections.
SS$_IVCHAN	An invalid channel number was specified; the channel number specified was 0 or a channel that is unassigned.
SS$_IVCHNLSEC	The channel number specified is currently active, or there are no files opened on the specified channel.
SS$_IVIDENT	An invalid channel number was specified; the channel number specified is larger than the number of channels available.
SS$_IVLOGNAM	The specified global section name has a length of 0 or has more than 43 characters.
SS$_IVLVEC	The specified section was not installed using the /PROTECT qualifier.
SS$_IVSECFLG	An invalid flag, a reserved flag, or an invalid combination of flags was specified.
SS$_IVSECIDCTL	The match control field of the global section identification is invalid.
SS$_LEN_NOTBLKMULT	The length_64 argument is not a multiple of virtual disk blocks.
SS$_NOPRMGBL	The process does not have the privileges to create or delete a permanent group global section (PRMGBL).
SS$_NOSYSGBL	The process does not have the privileges to create or delete a system global section (SYSGBL).
SS$_NOTFILEDEV	The device is not a file-oriented, random-access, or directory device.
SS$_NOWRT	The file is read only, and the flag bit SEC$M_CRF is not set.
SS$_OFF_NOTBLKALGN	The file_offset_64 argument is not a multiple of virtual disk blocks.
SS$_SECTBLFUL	There are no entries available in the system global section table.
SS$_TOOMANYLNAM	The logical name translation of the gs_name_64 argument exceeded the allowed depth of 10.

On Alpha and Integrity server systems, creates a permanent global page file section to which processes can map.

This service accepts 64-bit addresses.

Format

SYS$CREATE_GPFILE gs_name_64 ,ident_64 ,prot ,length_64 ,acmode ,flags

C Prototype

int sys$create_gpfile (void *gs_name_64, struct _secid *ident_64, unsigned int prot, unsigned __int64 length_64, unsigned int acmode, unsigned int flags);

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 32- or 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 2 bits. Their meanings are as follows:

Value	Symbolic 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. The version number 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.

prot

OpenVMS usage:	file_protection
type:	longword (unsigned)
access:	read only
mechanism:	by value

Protection to be applied to the global page file section. The mask contains four 4-bit fields. Bits are read from right to left in each field. The following diagram depicts the mask:

Cleared bits indicate that read, write, execute, and delete access, in that order, are granted to the particular category of user. Only read, write, and execute access are meaningful for section protection. Delete access bits are ignored. Read access also grants execute access for those situations where execute access applies. If 0 is specified, read access and write access are granted to all users.

length_64

acmode