Veritas File System 5.1 SP1 Administrator"s Guide (5900-1499, April 2011)

See the mount_vxfs(1M) manual page.
The log mode
In log mode, all system calls other than write(2), writev(2), and pwrite(2) are
guaranteed to be persistent after the system call returns to the application.
The rename(2) system call flushes the source file to disk to guarantee the
persistence of the file data before renaming it. In both the log and delaylog
modes, the rename is also guaranteed to be persistent when the system call returns.
This benefits shell scripts and programs that try to update a file atomically by
writing the new file contents to a temporary file and then renaming it on top of
the target file.
The delaylog mode
The default logging mode is delaylog. In delaylog mode, the effects of most
system calls other than write(2), writev(2), and pwrite(2) are guaranteed to be
persistent approximately 3 seconds after the system call returns to the application.
Contrast this with the behavior of most other file systems in which most system
calls are not persistent until approximately 30 seconds or more after the call has
returned. Fast file system recovery works with this mode.
The rename(2) system call flushes the source file to disk to guarantee the
persistence of the file data before renaming it. In the log and delaylog modes,
the rename is also guaranteed to be persistent when the system call returns. This
benefits shell scripts and programs that try to update a file atomically by writing
the new file contents to a temporary file and then renaming it on top of the target
file.
The tmplog mode
In tmplog mode, the effects of system calls have persistence guarantees that are
similar to those in delaylog mode. In addition, enhanced flushing of delayed
extending writes is disabled, which results in better performance but increases
the chances of data being lost or uninitialized data appearing in a file that was
being actively written at the time of a system failure. This mode is only
recommended for temporary file systems. Fast file system recovery works with
this mode.
VxFS performance: creating, mounting, and tuning file systems
Mounting a VxFS file system
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