Oracle Real Application Cluster (RAC) “is a product well known today in the solutions provided by Oracle to maintain high availability of the data of our business. Oracle RAC enables you to share the workload between all nodes in the cluster , resulting in a configuration with N-1 tolerance against failures of nodes, where N is the total number of nodes. Oracle RAC is constantly gaining improvements in each of its versions and this time was no different, in its new version 12c It incorporates two important features called “Flex ASM” and “Flex Cluster” that support the requirements demanded in environments oriented “Cloud Computing”.
“Flex Oracle ASM” ASM architecture changes with respect to previous versions of Oracle RAC. Before the introduction of “Flex Oracle ASM” in Oracle database version 12c, an instance of ASM existed in each of the nodes in the cluster, if one ASM instance failed, then all database instances running on the same node also fail.
Now, in the Oracle database version 12c, if an ASM instance fails, “Oracle Clusterware” starts a replacement ASM instance on a different node to maintain the cardinality of ASM.
The cardinality ASM default is three, but that can be changed with a few commands Clusterware.