The Windows Registry is probably the most long-lived source of annoyances in the IT industry. At the time of writing, it is fourteen years old, and still alive and well. However, developers have been growing more and more frustrated with the Windows Registry for the last few years, and things are supposedly about to change. This is what we are going to talk about today: will the Windows registry disappear?

As the complexity of applications and the size of the Windows Registry grew, developers started to have two main complaints about it: the single point of failure issue and the performance overhead introduced due to poor library design. The first one is impossible to circumvent; the other one can be circumvented, but at a cost.

The single point of failure (SPF) issue has to do with the fact that the registry plays an important role in the system, but it is not fail safe. It can be backed up and restored, but that has to be done manually, and if a registry file becomes corrupted, the system will not boot at all (in the worst case) or most of the user's settings will be lost (in the best case). Ironically enough, starting from Windows 2000, Windows does back up the registry automatically, but it still has to be manually restored which is a problem if you can't even boot into your system, a case in which you have to use the very unfriendly Recover Console.

The performance overhead does not just have to do with the registry itself. Initially it was thought that using a binary format would minimize the overhead: indeed, writing to a small binary file is faster than writing to a small, human-readable text file. But there's a catch: writing to a large binary file can be exquisitely slow compared to writing to a small text file. This was furthermore complicated by MFC -- Microsoft Foundation Classes, a very popular API used by developers. MFC allows the abstraction of application settings, allowing programmers to easily write and retrieve settings from the registry. Wonderful so far, with one exception: due to the way MFC and the registry work, when the value of one option is changed, all other options have to be written to the registry, even when they haven't been changed. Pair this up with a large set of registry files and you get quite an overhead.

So, what's the solution? Microsoft's recent development guidelines state that most per-application, non system wide settings should no longer be stored in the registry, but rather in a dedicated directory inside a user's home directory. You can see that yourself, it's the Application Data folder inside your home folder. This is intended to minimize the amount of data stored in the registry, retaining its advantages, but eliminating most of its disadvantages. Essentially, if the registry gets corrupted and is restored, the users do not lose any personal settings and applications run just as before the restoration.

However, if you have a look in the Application Data directory, you will notice that it is rather empty. This is for two reasons. First of all, the guidelines are slow to adopt. To this day, only a few important applications adhere to these standards, and even though their number increases, the Windows Registry is still very much used.

The other reason is that legacy applications still use the Windows Registry extensively. Eliminating the registry can be done in theory, but this would mean that no application which relies on the registry - that is, just about every Windows application would work or even install anymore.

Even if Microsoft does try to phase out the registry as we know it, this process will be very long-winded. We can expect the Windows Registry to be around for at least the following five or six years, with all its problems included. Until then, good registry cleaners such as RegCure or ErrorSmart will still find a dedicated audience, because until everyone decides to adhere to storing per-application, per-user settings in dedicated files, the registry will still be here to cause trouble.


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