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Oracle GNS and converting Grid Infrastructure from static DNS SCAN/VIP to dynamic GNS provided SCAN/VIP

Oracle GNS and converting Grid Infrastructure from static DNS SCAN/VIP to dynamic GNS provided SCAN/VIP

Note: As I did not see official Oracle documentation on the subject conduct thorough testing.

In the article you will have a look at the steps to convert already installed Oracle Grid Infrastructure based on static DNS SCAN and VIPs to dynamic GNS based where SCAN and node VIPs are provided by DHCP. You will refresh your understanding of GNS by briefly reviewing GNS concepts and benefits. You will look at the steps to set up and verify GNS configuration as a prerequisite for GNS implementation in existing Oracle 11.2.0.X GI/RAC installation.

Overview of GNS

Starting with release 11.2 Oracle introduced Grid Naming Service (GNS) functionality aiming at facilitating management of SCAN and nodes VIPs. GNS provides dynamic DHCP allocated addresses for the SCAN and nodes VIPs. For GNS to operate only one static address is required registered in the DNS that is for the GNS VIP. A sub-domain in DNS needs to be configured to perform delegation to the GNS, that is, queries for the defined sub-domain will be forwarded to GNS at the specified GNS VIP. DHCP is used to provide IP addresses. Due to the fact that DHCP does not provide a name to IP address mapping, mDNS is used to provide a DHCP IP address mapping to names. Within the cluster, nodes are using mDNS for name resolution while for servers outside the cluster DNS is used, which in turn forwards request to GNS. GNS acts as a gateway between DNS and mDNS and assists with name resolution of dynamically provided DHCP based IP addresses. The benefits of GNS are apparent in multi-node clusters where SCANs and node VIPs management is simplified and transparent for the administrator. In GNS configuration adding and deleting nodes is even simpler than with static DNS entries for the node VIPs.

If you have implemented RAC with static DNS initially, it makes sense to migrate to GNS if number of nodes increase.
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November 11, 2011 Posted by | oracle | 4 Comments