When we use Oracle RAC, all clients must be able to reach the database. All public addresses, VIP addresses and SCAN addresses of Cluster must be resolved by the clients.And GNS[Grid Naming Service] helps us resolve this problem.
GNS is linked to the domain name server (DNS) so that clients can resolve these dynamic addresses and transparently connect to the cluster and the databases. Activating GNS in a cluster requires a DHCP service on the public network.
Grid Naming Service uses one static address, which dynamically allocates VIP addresses using Dynamic Host Configuration Protocol[DHCP], which must be running on the network.
Grid Naming Service is in use with gnsd[grid naming service daemon].
Background Process of GNS: mDNS[Multicast Domain Name Service]: It allows DNS request.
GNS[Oracle Grid Naming Service]: It is a gateway between the cluster mDNS and external DNS servers. The GNS process performs name resolution within the cluster. The DNS delegates query the GNS virtual IP address and the GNS daemon responds to incoming name resolution requests at that address. Within the subdomain, the GNS uses multicast Domain Name Service (mDNS), included with Oracle Clusterware, to enable the cluster to map host names and IP addresses dynamically as nodes are added and removed from the cluster, without requiring additional host configuration in the DNS.
Note: From Oracle 12c, Oracle Flex Cluster requires Grid Naming Service (GNS).
Stay tuned for Oracle GNS Configuration
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