Recently we had what appeared to be a major issue occur on our Development AX environment. After performing a Synchronize on the Data Directory in the AOT, we received several warning messages, and then when attempting to view various forms we were receiving SQL errors, and what appeared to be missing data.
The initial assumption was that the Database had become corrupted. So we went through the process of doing a backup of the database in our Testing AX environment (which had no issues), and restoring it to the Development AX environment. After the restore however, we still received the same errors as before, which had us puzzled for a moment. Then my colleague, Tim Golisch, remembered something very important.
Not everything in AX is stored in the Database, in fact, everything relating to the layers, are actually stored in AOD files, which reside in the: C:\Program Files\Microsoft Dynamics AX\50\Application\Appl\[DB NAME] folder.
So I stopped the AOS, removed the axuser.aod file, started the AOS, opened the client, and wala! Everything was back to normal.