Monday, April 6, 2009

How Do I Decompile a Database?

Decompiling An Access Database

In order for any program code to be run by a computer, it must be converted to machine-readable code. This code is called Object Code. The text version of this program that you and I can read is called Source Code.

In Access, the process of producing Object Code from Source Code is called "compilation". Whenever code is run for the first time in Access, the code is first compiled. (You can also compile it yourself by pushing the compile button). The only place you can make changes to code is in the Source Code, which must again be compiled into Object Code.

Occasionally, code can be deleted from the Source Code, but for some reason is never removed from the Object Code. This code is never again seen on the screen as text, but is still sitting there somewhere in the database file. This can, at times, interfere with the normal operation of the program.

To remove these stray bits of code, you can "Decompile" your database and then re-compile it. This process removes all of the compiled Object Code, then when you re-compile it, you only get Object Code that reflects the current Source Code.

To Decompile your Access database, do the following:

  1. Click the Start button on the task bar and choose Run
  2. In the Run dialog box, type the following:
    "C:\Program Files\Microsoft Office\Office\Msaccess.exe" /decompile
    where the first part (in quotes) is the complete path to your Access program. If you have the default installation, it is likely that it is just as listed here. Click OK.
    Note: if you have Windows Vista, just type the command line in the Start Search box of the Start menu.
  3. This will open Access and allow you to choose which database to open. Whichever database you open will be decompiled.
  4. Choose a database and open it. Access 97 used to give you a dialog which told you the database had been decompiled, but newer versions do not. Nevertheless, the database has been decompiled.
  5. Open any Module in design view, or any Form or Report in design view and choose View > Code from the menu. In the next screen, choose Debug > Compile from the menu bar.
    Note: In Access 2007, you can also choose Database Tools on the ribbon, then select Visual Basic. Then choose Debug > Compile.
  6. Your database has now been Decompiled and Re-compiled.

Creating a Shortcut:

I use decompile quite frequently, so instead of typing the command line into the Run box, I've created a shortcut on my desktop. There are several ways to create a shortcut, the easiest is to use the Shortcut Wizard.

Right-click anywhere on your desktop and select New > Shortcut. The wizard will give you a dialog box allowing you to browse to the file you want. It should be the same as above in Step 2. Once you've browsed there, add the "/decompile" switch to the end as shown below. Be sure to separate the decompile switch from the file path with a space. It will look as follows:

Click Next.

It will ask to name your shortcut. Choose something descriptive like Decompile Access 2003. And click Finish.

The finished shortcut will look like this:

Now when I want to decompile a database, I just click the shortcut and start with Step 3 above.



Anonymous said...

For some technical information about decompiling visit Decompile or how to reduce Microsoft Access MDB/MDE size and decrease start-up times

Ingrid D said...

Thangs for the blog! This has saved me for sure. Once I got an error saying that the Function in the AutoExec could not be found. After decompiling and recompiling the issue went away...thanks again!!

Anonymous said...

This fixed my database. Thanks for a new trick!

sking said...

Bless you! I had no idea what was wrong. That fixed my database :-)I kept getting a return without gosub error on a function I had not changed and was working fine before

sking said...

Thank you so much for these directions! I kept getting a return without gosub error on a module that previously was not giving me problems. This fixed it.