AutoCAD 2009 Update 2 contains a small change to the way the DWG 2007 files are written to disk that optimizes how WAN acceleration hardware deduplicates 2007 DWG data. This will provide some performance gains for SAVE operations when users save across a WAN acceleration environment. The resulting 2007 DWG file will be readable whether or not other users also have AutoCAD 2009 Update 2 installed. However, to achieve the best performance, everyone working on the same DWG file should install AutoCAD Update 2 (or the relevant hotfix solution mentioned below).
After installing AutoCAD 2009 Update 2, you must set the Windows environment variable, ACADCOMPRESSIONMODE to 1 for the update to take effect.
To enable the WAN Acceleration improvement in 2007, 2008, or 2009 products that do not have Update 2 installed, refer to the following hotfix solutions:
WAN Acceleration 2009 Hotfix
WAN Acceleration 2008 Hotfix
WAN Acceleration 2007 Hotfix
Full documentation for installation and implementation is available in the Readme file included with the hotfixes.
WAN acceleration technology relies heavily on data-deduplication to accelerate data transfer. The 2007 DWG file format is written to disk using a type of error-checking that causes nearly every byte of the file to be changed during a full-save, even if the data itself was barely changed. WAN accelerators fail to deduplicate the 2007 DWG data and must transfer nearly all of the bytes contained in the 2007 DWG file. This results in a slow-down during full-save operations when working over a slow WAN.
Note: When using AutoCAD, you can often achieve performance gains in QSAVE operations by setting the ISAVEPERCENT system variable to 100. Doing so maximizes the chance that a QSAVE operation will use incremental-save rather than full-save. (WAN accelerator technology is able to achieve good performance in deduplication of 2007 DWG format files when an incremental save takes place.)