When you install a patch, the patchadd command copies files from the patch directory to a local system's disk. More specifically, patchadd:
Determines the Solaris version number of the managing host and the target host
Updates the patch package's pkginfo file with information about patches obsoleted by the patch being installed, other patches required by this patch, and patches incompatible with this patch
During the patch installation, patchadd keeps a log of the patch installation in /var/sadm/patch/patch-number/log for the Solaris 2.4 release and compatible versions. The Solaris 2.5 release and compatible versions also store log files in this location, but only if installation errors occurred.
The patchadd command will not install a patch under the following conditions:
The package is not fully installed on the host
The patch's architecture differs from the system's architecture
The patch's version does not match the installed package's version
There is already an installed patch with the same base code and a higher version number
The patch is incompatible with another, already installed patch. (Each installed patch keeps this information in its pkginfo file)
The patch being installed requires another patch that is not installed