Guardian Procedure Calls Reference Manual (G06.25+)

Guardian Procedure Calls (S)
Guardian Procedure Calls Reference Manual—522629-013
14-19
SEGMENT_ALLOCATE_CHKPT_ Procedure
filename:length input:input
STRING .EXT:ref:*, INT:value
indicates several types of swap files: temporary swap space using KMSF,
temporary swap file, existing permanent swap file, new permanent swap file, and
segment sharing by the file-name method
If
filename is specified, pin must be omitted.
•
Temporary swap space using KMSF
If you do not specify
filename or if you specify length as 0 (and if a
segment is not being shared using the PIN method),
SEGMENT_ALLOCATE_CHKPT_ uses the Kernel-Managed Swap Facility
(KMSF) to allocate swap space.
To share this segment, use the PIN method; you cannot use the file-name
method.
Performance is increased by using KMSF. However, if you want to save the
data in the segment after the process terminates, specify a permanent swap
file name. KMSF swap files have the clear-on-purge attribute, which provides
a level of security for swapped data.
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.