Oracle Flex Clusters 12c

Oracle Flex Clusters

Oracle clusterware technology was introduced in oracle 10g Release1 which transforming the server farms into a cluster. The cluster is group of independent servers connected with each other and acting as a single servers and is required to run the oracle Real Application Cluster(RAC).

In oracle 12c, the clusterware can be installed in one of the two ways.

1.) Standard Cluster:- Typical installation like pre 12c releases

2.) Oracle Flex Cluster :- New feature introduced in 12c which provides tightly and loosely coupled servers into a single cluster.

Oracle Grid Infrastructure installed in Oracle Flex Cluster configuration is scalable, dynamic and robust. It also provide the platform for variety of application which includes RAC with large number of nodes.

In oracle Flex Cluster, the nodes are arranged in two ways i.e. Hub Node and Leaf Node. The Hub Nodes are tightly connected with each other like standard configuration and have direct access to the shared storage. The maximum 64 hub nodes will be configured in a cluster. 

The leaf nodes can be added as many as more and can host different applications other than hub nodes. The leaf nodes doesn't require direct access to shared storage instead they can request data from Hub nodes. In Flex architecture, the shared storage can be provisioned to leaf nodes independently of Grid Infrastructure. The Hub nodes can be run or configured as member of cluster without any leaf nodes but leaf nodes must have Hub node to become member of cluster.

Flex Cluster Arch.

Installing Oracle Flex Cluster:- The oracle Flex cluster can be configured during fresh installation or you have flexibility to convert the existing standard cluster to oracle Flex cluster. Let us go with the fresh installation first,
Follow the prerequisites done in 12c Grid Infrastructure standard installations and proceed till steps 3 (Cluster Type).

On Step 3, select the cluster type as "Configure a Flex Cluster" and hit "Next" button.

In next window, select the preferred language or leave "English" as default, move "Next" window. Here provide the "Cluser Name", "SCAN Name" and "Port Number". Configure the GNS for flex cluster, Installation will fail if GNS is not configured with fixed VIP.

 In next window, select the cluster nodes by select "Add" button and provide the public name, their role and virtual name. Here you have opportunity to setup the SSH. Then click "Next" button.

Select the correct Network Interface and the type. Here i am using dedicated network interface for ASM. but you can also use the cluster interface for ASM as well be select the "private&asm". Hit the "Next" button to move further.

 The next window will provide you the option to create "Grid Infrastructure Management Repository", select you choice and move further.

From here onwards, the steps same as standard type installation, follow the 12c Grid Infrastructure installation and proceed further till the End.

Verification :->
[grid@Node2 bin]$ ./crsctl get cluster mode status
Cluster is running in "flex" mode
[grid@Node2 bin]$
[grid@Node2 bin]$ ./srvctl status asm -detail
ASM is running on node1,node2,node3
ASM is enabled.
[grid@Node2 bin]$ ./srvctl config asm
ASM home: /orasoft/app/grid/12.1.0/grid
Password file: +DATA/orapwASM
ASM listener: LISTENER
ASM instance count: 3
Cluster ASM listener: ASMNET1LSNR_ASM
[grid@Node2 bin]$