Error 0x80004005: “Could not use ‘(unknown)’; file already in use” when using Microsoft Access databases in conjunction with IIS, Dreamweaver and others

System Requirements:

• An Access database
• Internet Information Services (IIS) 4.0, 5.0, 5.1, 6.0, 7.0
• Dreamweaver

The Problem:

This error can arise for a variety of reasons, however the specific one which prompted me to write this was to do with using IIS and Dreamweaver to fiddle with its ‘Application’ management system for connecting to and inserting dynamic information onto web pages.

When you attempt to use the database you receive the following error message in your web browser:

This occurs despite giving the IUSER_<system_name> account permissions to access the MDB file.

The Fix:

This could be:

• A bad/corrupt MDAC install
• An old MDAC install; ensure you are using 2.8
• An old version of JET – ensure that you have the latest 2000/XP/2003 service pack or have installed Jet 4.0 SP8 on anything else

However is is more likely that you are running into a permissions error (yes, even though you gave the IUSR_<system_name> permissions on the MDB).

When you are using an Access database, of course the IIS service account IUSR_<system_name> needs to have correct permissions on the .MDB file that you are using. This goes without saying.
If you haven’t got that far, ensure that you have disabled simple file and folder sharing (on XP Pro) and offer up modify permissions or higher (do so with care) on the .mdb, however this will not solve the error!

When you use an Access database, during that fleeting second when the database is being structurally polled, Access will lock the database to prevent concurrent activity from taking place, however it does this in a relatively unsophisticated manner using a file-system flag.

By default Access will attempt to create the file system flag, a .LDB file named in an identical fashion to that of your database next to the .MDB. The problem is that the LDB is being written using the IUSR_<system_name> account which under Windows 2000 will be part of the everyone group, and has more secure default permissions under later version.

What is happening is that your system is either unable to create the LDB because of a permissions conflict, or more likely in the case of you receiving the error listed at the beginning of this article it is creating the LDB file, but is unable to clear the file-system flag.

In other words: Access is locking the database, but in its crudeness is unable to unlock it!

You must ensure that you have set the necessary permissions on the database folder/directory with the permissions on the folder inheriting down to the files contained within it.

Now that you have a folder with write/modify (or worse) permissions for the IIS process/guest account, you need to think about security. Never, ever put the database folder beneath the public wwwroot of the site. Always place the database directory at the bottom of a folder hierarchy and always keep your permissions as tight as possible.