Ref: 08720024
Title: Using the DOS Enhanced LANMAN.INI OPTIMIZATIONS= Parameter
Date: 12/13/90

Copyright 3Com Corporation, 1991.  All rights reserved.

The DOS Enhanced LANMAN.INI OPTIMIZATIONS= parameter is a bitmask field
that controls the behavior of the DOS Enhanced redirector.  Four features
are controlled by the value of this parameter.  These four features are
logically OR'ed together to create the value of the OPTIMIZATIONS= parameter.
These features and their bitmasks are

   Use Write Behind   0001b
   Use Write&X Behind 0010b
   Use AsyncReadAhead 0100b
   Use WriteRawData   1000b

Thus, the default value of 3 is 0011b or Use WriteBehind OR'ed with
Use Write&X Behind.  Write&X commands are single commands that tell
the server to perform two seperate operations, such as Write&Unlock
or Write&Close.

Write-behind is where the redirector will immediately tell the
requesting application that the write operation has completed
successfully, even though it has not completed yet.  The application can
then continue rather than wait for the write operation to complete.  The
redirector will attempt to complete the write operation on its own.

AsyncReadAhead, when enabled, allows the redirector to request an
entire block of data when the application asks for less than an entire
block.  The extra data will be cached within the redirector in
anticipation of the application requesting additional data sequentially.

WriteRawData allows the workstation redirector to transfer the data to
the server in a raw form.  No header or checksum information is
generated, which makes the data transfer extremely fast but does not
allow error detection or correction to be performed.

Under medium to heavy network loads 3Com has discovered that network
problems can occur if the redirector is allowed to use Write&X Behind.
The redirector will always report success immediately, but may sometimes
fail to successfully write the data to disk at a later point in time.  The
symptoms of this are less than optimal performance or NET808 errors at
the workstation.

3Com recommends that all DOS Enhanced workstations be modified so that
the value of OPTIMIZATIONS= they are using is 1 (use Write Behind only).

Under certain circumstances, such as copying large files to a nearly
full hard disk on the server, errors can occur even when the value of
OPTIMIZATIONS= is set to 1 (use Write Behind).  To prevent any errors
from occurring due to optimizations, you can change the value of the
parameter to 0 (perform no optimization).

3Com will change the default value of this parameter to 1 with the 3+Open
1.1F Maintenance Update.

