HP JFS 3.3 and HP OnLineJFS 3.3 VERITAS File System 3.3 System Administrator's Guide

78 Chapter3
Extent Attributes
Attribute Specifics
Reservation Trimming
A reservation request can specify that any unused reservation be
released when the file is closed. The file is not completely closed until all
processes open against the file have closed it.
Reservation Persistence
A reservation request can ensure the reservation does not become a
persistent attribute of the file. Unused reservation is discarded when the
file is closed.
Including Reservation in the File
A reservation request can make sure the size of the file is adjusted to
include the reservation. Normally, the space of the reservation is not
included in the file until an extending write operation requires it. A
reservation that immediately changes the file size can generate large
temporary files. Unlike a ftruncate operation that increases the size of
a file, this type of reservation does not perform zeroing of the blocks
included in the file and limits this facility to users with appropriate
privileges. The data that appears in the file may have been previously
contained in another file.