I think the 11G RAC instances communicate more than under 10G. You can try to look in ASH which statements are connected with this wait.
Von: firstname.lastname@example.org [email@example.com]" im Auftrag von "CRISLER, JON A [JC1706@att.com]
Gesendet: Dienstag, 7. Februar 2012 16:56
Betreff: Wait Event - rdbms ipc message
Oracle RAC 11g, AWR reports shoes the metric "rdbms ipc message" as the #1 in Top 5 wait events.
I have to admit I don't think I have seen this before, and I am not sure where to look-
11gR2 on Red Hat Linux 5 64 bit, ASM to SAN.
Any suggestions ?