Sriram, even on PA-RISC, HMP seems also not supported with 10gR2. See : Oracle Clusterware and Oracle Real Application Clusters Installation Guide 10g Release 2 (10.2) for HP-UX B14202-03 (December 2005) <Quote> Note: UDP is the default interconnect protocol for RAC, and TCP is the interconnect protocol for Oracle Clusterware. Token-Ring is not supported for the interconnect. At the time of this release, Hyper-Messaging Protocol (HMP) is not supported. </Quote> Selon Sriram Kumar <k.sriramkumar@xxxxxxxxx>: Hi Gurus, We are presently using a HP Itanium2 cluster running Oracle 9i RAC. We are to migrate soon to 10g RAC. Was surpised to find a note in metalink that says that HMP is not supported in Oracle 10g RAC. Note id 220970.1 <Quote> Is HMP supported with 10g on all HP platforms ? - 10g RAC + HMP + PA-RISC = yes - 10g RAC + HMP + Itanium, "Oracle has no plans and will likely never support RAC over HMP on IPF." - 10g RAC + UDP + Itanium = yes (even over Hyperfabric) "Oracle recommends that HMP not be used. UDP is the recommended interconnect protocol across all platforms." <Unquote> When we migrated to Oracle9i RAC, we were said (rather pushed) that HMP would be much better that UDP and we bought expensive HyperFabric switches and now Oracle cooly says HMP is not supported now we will have to run UDP on these HyperFabric switches Thought this would help others in the list using HMP or planning to buy Hyper Fabric Best Regards Sriram Kumar -- //www.freelists.org/webpage/oracle-l