First Impression of Oracle 11gR2 RAC

11g Release 2 RAC has some major changes from 11g Release 1.

For starter, ASM and Clusterware are combined into single Oracle binary home called Oracle grid infrastructure. By default, the voting disks and OCR are in ASM diskgroup instead of raw devices recommended in previous releases. Such change contradicts the concept that ASM is on top of clusterware for previous releases and raise question such as, if ASM is crashed, does clusterware service dies as well because voting disks and OCR are not accessible? Well, the clusterware can access voting disks directly without going through ASM, so it will bring up ASM automatically after it is crashed. Restore an OCR is more difficult and requires to shutdown clusterware on all nodes, then start clusterware on one node exclusively with ASM online. Fortunately, OCR is not easy to corrupt because it is in a normal redundancy diskgroup or high redundancy diskgroup.

Another new feature of 11g Release 2 is SCAN (Single Client Access Name) which binds round-robin dynamic DNS to RAC nodes. It provides easy way of load balance and failover for any client connection. However, it could be a challenge to setup DNS and I wish the installation can have an option not to use SCAN for RAC.

Overall, release 2 RAC is easier to install and deinstall than that of earlier release and more stable because of cluster time service. It also has better scalability than earlier release because the performance improvement of inter-node communication.