I have also compiled a list for Sun Cluster updates vs release date;
Sun Cluster 3.0 – initial release
u1 7/01
u2 5/02
u3 12/01
Sun Cluster 3.1 – initial release 5/03
u1 10/03
u2 4/04
u3 9/04
u4 8/05
Sun Cluster 3.2 – initial release
u1 2/08
u2 1/09
u3 11/09