Real Application clusters on 11g

Oracle Database 11g Release 1 (11.1) New Features in Oracle Real Application Clusters
This section describes the Oracle Database 11g release 1 (11.1) features for Oracle RAC administration and deployment.
Oracle Clusterware administration content moved to a separate book
Oracle Clusterware administration is now documented in a separate book.
Oracle cloning procedures for ASM and Oracle RAC Databases
A new chapter provides step-by-step procedures for cloning Oracle Automatic Storage Management (ASM) and Oracle RAC homes to quickly extend ASM and Oracle RAC environments to additional nodes with the same configuration.
Parallel execution processes run on database instances according to service placement
Parallel execution is now aware of the service definition and automatically takes on the appropriate PARALLEL_INSTANCE_GROUPS setting, making it unnecessary to explicitly set the PARALLEL_INSTANCE_GROUPS initialization parameter for an Oracle RAC database. Thus, if you execute a SQL statement in parallel, then the default behavior is for Oracle to run the parallel processes only on the instances that offer the service that you used to connect to the database.
Extending ASM to Nodes Running Single-Instance or Oracle RAC Databases
Using the Database Configuration Assistant (DBCA), you can now add a new ASM instance to a node that is running either a single-instance database or an Oracle RAC database instance.
OCI Runtime Connection Load Balancing
OCI session pools have a new feature called Runtime Connection Load Balancing. OCI session pools are now integrated with the Oracle RAC load balancing advisory to provide load balancing at the time the application gets the connection from the session pool.
Enhanced support for XA transactions in Oracle RAC environments
An XA transaction can now span Oracle RAC instances, allowing any application that uses XA to take full advantage of the Oracle RAC environment. This feature allows the units of work performed across these Oracle RAC instances to share resources and act as a single transaction.
Automatic Database Diagnostics Monitor (ADDM) enhancements for Oracle RAC and Enterprise Manager support
ADDM has been enhanced to provide comprehensive clusterwide performance diagnostic and tuning advice. This enhanced mode of ADDM, called ADDM for Oracle Real Application Clusters, analyzes an Oracle RAC database cluster and reports on issues that are affecting the entire cluster as well as those affecting individual instances.
This feature is particularly helpful in tuning global resources such as I/O and interconnect traffic, making Oracle RAC database management easier and more precise.
In addition, Oracle Enterprise Manager supports ADDM enhancements for Oracle RAC:
ADDM database-wide analysis for Oracle RAC.
oTargeted ADDM analysis is available for several granularity levels, such as the cluster database, database instance, or for specific targets such as SQL, sessions, services, modules, actions, clients, or wait classes.
ASM preferred mirror read
This feature is useful in extended clusters where remote nodes have asymmetric access with respect to performance. This leads to better storage utilization and lower network loading.ASM in Oracle Database 10g always reads the primary copy of a mirrored extent set. In Oracle Database 11g, when you configure ASM failure groups it might be more efficient for a node to read from a failure group extent that is closest to the node, even if it is a secondary extent. You can do this by configuring preferred read failure groups.