An archive of the most necessary patches to a base install of Solaris (or whatever). It includes an installer script to automate said process. It is not uncommon for the big mish-mash of patches in a patch set to screw with the proper functioning of a previously working machine. The nomenclature used by Sun for these archives is usually nnn_Recommended.zip, where 'nnn' is the release version of the OS. Recommended patch sets can be found at sunsolve.sun.com .