The following applies to latest "October 2005 stream". Note that Linux distributions containing code based on this stream (like Novell SUSE SLES10 and Red Hat RHEL5) have their own documentation on prerequisites. For Linux distributions you may find the webpage on IBM tested Linux environments useful.
IBM service and support is available for
for Linux on System z running:
Starting with the "October 2005 stream" IBM supports only 64-bit distributions;
31-bit applications are supported on the 31-bit emulation layer.
IBM System z (or System z, for short) is used on these pages when referring to the above mentioned mainframes.