System Administration Guide, Volume 1

What Happens When You Remove a Patch

When you back out a patch, the patchrm command restores all files modified by that patch, unless:

The patchrm command calls pkgadd to restore packages that were saved from the initial patch installation.

During the patch removal process, patchrm keeps a log of the back out process in /tmp/backoutlog.process_id. This log file is removed if the patch backs out successfully.