There are a number of reasons why a patch may become obsolete; for instance, a newer version of it may have been released, or a different patch that replaces the obsolete one may have been installed.
When this happens, the original patch files will remain on the system, but the undo file will be renamed “obsolete.” A file named obsoleted_by will also be created that contains the ID of the new patch.
Let's take a look at how this works. The following steps show how the files are manipulated by installing the newer patch. For this example, we already have 105463-06 on the system and have just installed 105463-07:
hydrogen# patchadd -p | grep 105463 Patch: 105463-06 Obsoletes: Requires: Incompatibles: Packages: SUNWvxvm Patch: ...