|Windows Installer Basics: Patches|
A patch is similar to a transform but built in a completely different manner and applied after the product is installed (not during the install).
The major advantage of a Windows Installer patch (over "traditional" patches is that Windows Installer patches an installed product). This is also its disadvantage as it is a lot of work to do this.
Please see the "Patch Creation" section for some information about how patches can be created.
A failure of a full upgrade patch to apply can also result in the product being removed, not in its original state (its not "rolled back"). This of course requires the user to reinstall the original product before attempting the patch again.
The contents of a patch file (.msp) file can be examined with "ORCA" and "MsiDiff.VBS". The patch applicability browser will help you identify what products a patch can be applied to.
|Links to Patch Related Pages|
|My 2 cents Worth|
You may wish to read my "Patches and Non-Major Updates can be dangerous!" page!
I think that while the Windows Installer way of patching does have some advantages, it is dangerous as it requires too much extra in the way of skills, development work and testing for what should be a relatively simple process that doesn't need a huge amount of separate testing (or integration with the installer).
The "RTPatch" program is an example of a program that can generate patches that require much less in the way of skills and the patch testing can be a much smaller component of the overall development and testing.
Also note that years ago I wrote a patch program which I will have to dig up.