Wednesday, September 17, 2008

WAN acceleration hotfix for AutoCAD products and DWG files

This hotfix improves performance of save to 2007 DWG format when running in a WAN Acceleration environment.

This is great news after the problems earlier described:

Description of Problem

WAN acceleration technology typically relies on data-deduplication as a significant part of accelerating data transfer. The 2007 DWG format is written to disk with a type of error-checking that has the side-effect of nearly every byte of the file changing during full-save, even if little was changed. WAN accelerators fail to deduplicate the 2007 DWG data and must transfer nearly all bytes in the 2007 DWG file. This results in a slow-down during full-save when working over a slow WAN.

The Solution

This hotfix will make a small change in the way the 2007 format DWG files are written to disk such that WAN acceleration hardware will be better able to deduplicate the 2007 DWG data; this will provide some performance gains for SAVE operations when users are saving across a WAN acceleration environment. The resulting 2007 DWG file will be readable whether or not others have this hotfix, but to achieve the best performance everyone working on the same DWG should install this hotfix.

After installing the hotfix, you must set the Windows environment variable, ACADCOMPRESSIONMODE to 1 for it to have effect.

Note: For AutoCAD, you can often get performance gains in QSAVE operations by setting the ISAVEPERCENT system variable to 100. Using a value of 100 will maximize the chance that a QSAVE operation will use incremental-save rather than full-save. (WAN accelerator technology is able to show good performance in deduplication of 2007 DWG format files when incremental save takes place.)


Make sure to read the Readme on how to install acdb17.dll and AcSignCore16.dll and set the ACADCOMPRESSIONMODE environment variable.


  1. Very useful informative post.Thank you.

  2. AutoCAD 2009 Update 2 includes this hotfix.
    Knowledge Base document: WAN Acceleration Hotfix


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