Oracle 11gR2 New Features for RAC

The Basics: The clusterware is now known as Grid Infrastructure. CRS and ASM binaries reside under a single Oracle Home known as GRID Home. GRID Home and the Oracle Home must be installed in different locations. Oracle Grid Infrastructure cannot be placed under Oracle Base since permissions will be changed to root. OCR and Voting File can no longer be placed on RAW or block devices. They need to be placed either in ASM or on Shared NFS Storage. Voting file does not need to be backed up using dd command and is not supported anymore.The contents of Voting file are backed into the OCR. For more details on the architecture and understanding of background processes, refer Metalink Note: 1053147.1 SCAN: Single Client Access Name(SCAN) as the name suggests is a single name for clients to access RAC database. The obvious benefit is as nodes get added to the cluster, client TNS remains unchanged. It's like a virtual load balancer. You can find more details on Metalink Note:887522.1 Always remember the following about SCAN during your RAC installation: SCAN name can be maximum up to 15 characters excluding the domain name. Keep this in mind while requesting for scan name and IPs otherwise you won't be able to proceed with your installation since SCAN is a mandatory requirement. Ask your clients to use 11gR2 version of client coz with older version(11gR1/10gR2), if one of the SCAN listener goes down, the connection will fail. Only 11gR2 client will give full functionality of SCAN. You can have workarounds though by explicitly specifying all the 3 SCAN IPs in the client TNS. Set REMOTE_LISTENER to SCAN. DO NOT set to TNSNAMES alias. Example: remote_listener='scan-clu:1521'. Default installation will not update remote_listener and it's imperative to set it correctly if you wish your clients to use single name in the TNS. LOCAL_LISTENER should be set to node VIP as FQDN(Fully Qualified Domain Name). Default install would put the VIP but not as fully qualified. FQDN is important otherwise you may notice intermittent connection failures. Best way to troubleshoot SCAN is to set ORACLE_HOME to GRID_HOME since SCAN listener runs from Grid Home and check for 'lsnrctl servics SCAN_LISTENER' to verify if all instances are registered correctly.