Users installing AIX Version 4.3 who are concerned about binary compatibility with AIX Version 3.2 should install the compatibility filesets offered on the installation media. These filesets offer commands, library versions, symbolic links and other items that, when added to the system, make it look more like a AIX Version 3.2 system from an application point of view.
While some of these filesets increase disk requirements (substantially, in the case of the AIXwindows X11R3 and R4 compatibility packages) and contain obsolete function, the compatibility filesets increase portability in an environment with machines running mixed levels of AIX. Installing the compatibility filesets is highly recommended.
If you performed a Migration Installation, you do not need to install these filesets.
Use the instructions in "Installing Optional Software and Service Updates" to install these filesets. The filesets are listed with compat in the name. For example, the bos.compat.cmds fileset contains the base operating system compatibility commands, and the X11.compat.lib.X11R3 fileset contains the AIXwindows X11R3 compatibility libraries.