Guardian Procedure Calls Reference Manual

For more information on this facility, see the Kernel-Managed Swap Facility (KMSF) Manual.
• Temporary swap file
If supplied, if length is not 0, and if filename is a volume name without a subvolume
or file identifier, SEGMENT_ALLOCATE_CHKPT_ creates a temporary swap file on the
indicated volume. If you specify a system name, it must be the system name of the local
node. You can convert a temporary file to a permanent file by renaming it with the
FILE_RENAME_ procedure.
If you do not specify filename and bit 13 of the alloc-options parameter is set to
1, SEGMENT_ALLOCATE_CHKPT_ creates a temporary swap file on a volume that it
chooses.
• Existing permanent swap file
If supplied and if length is not 0, specifies the name of a swap file to be associated with
the segment. If used, the value of filename must be exactly length bytes long. If the file
name is partially qualified (for example, without the volume name), it is resolved using the
contents of the =_DEFAULTS DEFINE. All data in the file is used as initial data for the
segment. Remote file names, structured files, audited files, and files with the refresh attribute
are not accepted.
There are two advantages of using an existing swap file. First, if the file is the required
size, segment allocation cannot fail due to lack of disk space. Second, the segment becomes
a permanent repository of data.
If the process terminates without deallocating the segment, any data still in memory is
written back out to the file. Unless the segment is extensible, SEGMENT_ALLOCATE_CHKPT_
must be able to allocate a sufficient number of file extents to contain all memory in the
segment.
• New permanent swap file
If supplied, if length is not 0, and if filename does not exist, specifies the name of a
swap file to be created. If used, the value of filename must be exactly length bytes
long. Remote file names are not accepted.
The advantage of using a permanent swap file is that the segment becomes a permanent
repository of data.
If the process terminates without deallocating the segment, any data still in memory is
written back out to the file. Unless the segment is extensible, SEGMENT_ALLOCATE_CHKPT_
must be able to allocate a sufficient number of file extents to contain all memory in the
segment.
• Segment sharing by the file name method
By specifying filename, you can share the segment associated with this swap file with
another process using the same swap file (provided that both processes have appropriate
permission to the file). This is referred to as segment sharing by the file-name method. Two
processes sharing a segment by the file-name method must be in the same processor,
unless the segment is a read-only segment. (See the SEGMENT_ALLOCATE_ procedure
Considerations (page 1268).)
SEGMENT_ALLOCATE_CHKPT_ Procedure 1273