We came across an issue recently where we had the same GUID for two different AX installations running on the same server and therefore only one AUC file existed for both installations instead of two separate ones for use by the AX Client.
This caused various anomalies when the client was used to access both instances. We expect each of the AX installations having their own separate objects and application files associated to the AUC file.

In order to ensure that a unique AUC file is created per instance for the AX client to use, and also to ensure that the AX instances had a unique Global GUID, the solution was to delete the GlobalGUID from the SysSQMSettings table in one of the instances and replace the value with an empty GUID (00000000-0000-0000-0000-000000000000).
Then restart the AOS service, as this will then generate a new GUID and allows a new AUC file to be created for the AX client when it is next run.

The above problem was most likely caused by using a copy of the same database.



Further information

What is an AUC file?

AUC means application Unicode object cache. The .auc file contains cached data for the Microsoft Dynamics AX Windows client application on the client computer.

Location of AUC cache files

The auc file is usually found here:

  • Windows XP / Windows Server 2003
    %USERPROFILE%\Local Settings\ApplicationData (this is a hidden folder).

  • Windows Vista / Windows 7 / Windows Server 2008 / Windows Server 2008 R2
    %USERPROFILE%\AppData\Local (this is a hidden folder).

Naming of AUC files

Differences between AX 4.0 and AX 2009:
The naming of the AUC file is different in AX 3.0, AX 4.0 and AX2009.
In AX2009 we use a GUID as unique identifier while in AX 4.0 the file name has been built from server name and user name and in AX 3.0 from AOS name, server name and user name. Additionally before AX 4.0 the extension was AOC (Application Object Cache).

  • Example of cache file name in AX 3.0:
    ax_Axapta@MyServer_Admin.aoc
    ax_ [aos object server] @ [server] _ [user] .aoc
  • Example of cache file name in AX 4.0:
    ax_MyServer_Admin.auc
    ax_ [server] _ [user] .auc
  • Example of cache file name in AX 2009:
    ax_{7998C152-49DD-48E4-A9F8-FA1BC3FB4AE7}.auc
    Where {7998C152-49DD-48E4-A9F8-FA1BC3FB4AE7} is a unique GUID.

Where is the GUID coming from?

The GUID is stored in the SysSQMSettings table and is unique for each AX installation.
You can find it by using the following Select statement:

select GlobalGUID from SysSQMSettings


Is there a solution for AX 4.0?

Currently there exists no solution for AX 4.0 installations beside the recommendation to not install multiple AX 4.0 versions on the same machine.
One workaround could be to create a small DOS batch that first deletes the AUC file and then starts the AX Client.