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12c Database : Convert normal cluster to flex cluster

Continuing from previous post,

Prerequisites for FlexCluster:-
  1. You must use Grid Naming Service (GNS) with an Oracle Flex Cluster deployment.
  2. You must configure the GNS VIP as a static IP address for Hub Nodes.
  3. On Multi-cluster configurations, you must identify the GNS client data file location for Leaf Nodes. The GNS client data files are copied over from the GNS server before you start configuring a GNS client cluster.
  4. All public network addresses for both Hub Nodes and Leaf Nodes, whether assigned manually or automatically, must be in the same subnet range.
  5. All Oracle Flex Cluster addresses must be either static IP addresses, DHCP addresses assigned through DHCP (IPv4) or autoconfiguration addresses assigned through an autoconfiguration service (IPv6), registered in the cluster through GNS.
Enabling Flexcluster:-

1. Via Installation, the first screenshot

Rac12c1 2013 07 30 22 56 04

2. Via CRSCTL command

Determine the existing cluster mode, ensure the GNS is configured with a fix VIP:

$ crsctl get cluster mode status

$ srvctl config gns | srvctl status gns

As root user, configure GNS with a fix VIP when no GNS is configured currently, and start GNS subsequently:

$ srvctl add gns -vip <rac1_gns_vip> -- can be used virtual hostname or IP here

$ srvctl start gns

As root user, run through the following commands to switch the current mode to Flex Cluster mode:

$ crsctl set cluster mode flex

$ crsctl stop crs -- this should be done on all nodes

$ crsctl start crs -use [-wait] option to display progress message

Modifying the node role i.e Hub or Leaf:-

1. While installation, select the nodes as hub or leaf

2. Via CRSCTL command

While the clusterware is up and running

After the cluster startup, change the node roles, HUB|LEAF accordingly, run through the following commands as root user:

$ crsctl get node role config

$ crsctl set node role hub|leaf

$ crsctl stop crs

$ crsctl start crs

$ crsctl status service node –f – shows the node role leaf or hub

Important Notes:-

  1. Once the cluster is moved to Flexcluster, you cannot revert to standard mode,
  2. The node roles can be modified i.e leaf to hub and vice versa.
  3. FlexASM is required before you enable flexcluster. See flexasm
  4. The database nodes should not be set as leaf node, the cluster crs will fail to start the service since there is a hard dependency on asm storage for voting disk and ocr, see error below if you do so.
  5. If there is no GNS the flexcluster mode will not be able to start up, the log throws the following error

Happy Reading,


Geek DBA

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