Wyse WintermTM 9000 Benutzerhandbuch

The write filter provides a secure environment for thin-client computing. It does this by 
protecting the terminal from undesired flash memory writes (flash memory is where the 
operating system and functional software components reside). The write filter also 
extends the life of the terminal by preventing excessive flash write activity. It gives the 
appearance of read-write access to the flash by employing a cache to intercept all flash 
writes and returning success to the process that requested the I/O.

The intercepted flash writes stored in cache are available as long as the terminal remains 
active but will be lost when the terminal is rebooted or shut down. To preserve the results 
of writes to the registry, favorites, cookies, etc., the contents of the cache can be 
transferred (“flushed”) to the flash on demand by the Rapport Remote Administration 
Software or manually using the Write Filter Control dialog box (see Figure 12) available 
from the Control Panel | Administrative Tools | Write Filter selection or through the 
Start menu. After the write filter has flushed the cache, all future writes during the current 
boot session are written to the flash, with no further caching until a reboot occurs. The 
write filter may also be enabled/disabled through the command line or through the Write 
Filter Control dialog box. The enabled/disabled status of the write filter is displayed on 
the green/red button icon on the task bar system tray (green indicates that the write filter is 
active, and red indicates that the write filter is inactive).

The administrator should periodically check the status of the cache. The terminal should 
be rebooted if the cache is more than eighty percent full.

When administering the terminal for permanent changes, to avoid flash 
corruption it is strongly recommended flushing the write filter cache 
immediately following a fresh reboot before making permanent modifications 
to the system. Do not flush the cache if the terminal has been used in the 
current boot session.

The write filter cache should never be flushed if it is eighty-percent or more 
full.

The write filter can be manipulated through the command line or the Write Filter Control 
dialog box, as follows:

Command line arguments cannot be combined.

Terminal Administrators should use NT file security to prevent undesired 
usage of these commands.