I'm using WiX 3.5. Recently, the following WiX error started occurring frequently on the build server:
light.exe (,): error LGHT0301: Failed to open the database. During validation, this most commonly happens when attempting to open a database using an unsupported code page or a file that is not a valid Windows Installer database. Please use a different code page in Module/@Codepage, Package/@SummaryCodepage, Product/@Codepage, or WixLocalization/@Codepage; or make sure you provide the path to a valid Windows Installer database.
Which "database" does the error refer to? (None of the WiX source files have changed in a long time, so I doubt it's a code page problem.)
Other people have reported that this error may be caused by Trend Micro Office Scan, which is indeed installed on the build server. I asked the system administrator to exclude the build directories from the scan, but this error still occurs. How can I determine whether the virus scanner is the culprit? (The error doesn't always occur, so if I disable the virus scanner and the next build succeeds, I still don't know whether the error has gone away permanently.)
After studying the WiX source code and running Process Monitor, I found that excluding the build directories from the virus scan is insufficient.
Explanation: When light.exe runs, it creates the target MSI file in a temporary directory. (This file is the database that the LGHT0301 error message refers to.) After light.exe closes the MSI file, ntrtscan.exe opens the MSI file for read access and read-only sharing. Later, in the database validation step, light.exe tries to reopen the MSI file for read/write access, and a sharing violation occurs.
Solution: Exclude the temporary directory from the real-time virus scan. On Windows Server 2008, for example, this directory is C:\Users\«username»\AppData\Local\Temp.