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Some new concepts in 11gR2 Rac

Oracle clusterware and ASM now are installed into the Same Oracle Home, and is now called the grid infrastructure install.

Raw devices are no longer supported for use for anything (Read oracle cluster registry, voting disk, asm disks), for new installs.

OCR and Voting disk can now be stored in ASM, or a certified cluster file system.

The redundancy level of your ASM diskgroup (That you choose to place voting disk on) determines the number of voting disks you can have.
You can place

Only One voting disk on an ASM diskgroup configured as external redundancy
Only Three voting disks on an ASM diskgroup configured as normal redundancy
Only Five voting disks on an ASM diskgroup configured as high redundancy


The contents of the voting disks are automatically backed up into the OCR

ACFS (Asm cluster file system) is only supported on Oracle Enterprise Linux 5 (And RHEL5), not on OEL4.

There is a new service called cluster time synchronization service that can keep the clocks on all the servers in the cluster synchronized (In case you dont have network time protocol (ntp) configured)

Single Client Access Name (SCAN), is a hostname in the DNS server that will resolve to 3 (or at least one) ip addresses in your public network. This hostname is to be used by client applications to connect to the database (As opposed to the vip hostnames you were using in 10g and 11gr1). SCAN provides location independence to the client connections connecting to the database. SCAN makes node additions and removals transparent to the client application (meaning you dont have to edit your tnsnames.ora entries every time you add or remove a node from the cluster).

Oracle Grid Naming Service (GNS), provides a mechanism to make the allocation and removal of VIP addresses a dynamic process (Using dynamic Ip addresses).

Intelligent Platform Management Interface (IPMI) integration, provides a new mechanism to fence server’s in the cluster, when the server is not responding.
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