RAC Attack - Oracle Cluster Database at Home/RAC Attack 12c/Flex Cluster and Flex ASM


The purpose of this particular is to illustrate a conversion from standard to flex for both Cluster and ASM. Although the names Flex Cluster and Flex ASM appear similar, they are two distinct and for the most part mutually exclusive, components of RAC in 12c.

Flex ClustersEdit

Flex Clusters Illustration

Flex Clusters introduces (among many other new features) the concept of Hub and Leaf nodes.

Hub NodesEdit

Hub Nodes are similar to Oracle Grid Infrastructure nodes in an Oracle Clusterware standard Cluster configuration.

Leaf NodesEdit

Leaf Nodes are different from standard Oracle Grid Infrastructure nodes, in that they do not require direct access to shared storage, but instead request data through Hub Nodes.

Leaf and Hub Nodes in Flex Cluster

Leaf nodes were designed to contain application (non-database) components of a system. For example, one could place Fusion Middleware, EBS, IDM etc on a set of leaf nodes, where as on the hub nodes the actual databases for the application would reside.

For a standard cluster to covert to a Flex Clusters, Flex ASM must be enabled.

Flex ASMEdit

Oracle Flex ASM enables Oracle ASM instances to run on a separate physical server from the database servers. An Oracle ASM instance can operate in several configurations in Oracle Flex ASM. The aim of Flex ASM is to consolidate ASM instances into a set of nodes within a cluster.

Flex ASM


This lab assumes that the user has an existing 2-node RAC environment configured as per the base RAC Attack 12c manual instructions.