Grid Plug and Play Information

Grid Plug-and-Play

Oracle Grid-Plug-and-Play framework provides an operational environment for Oracle Grid Infrastructure that eliminates having to configure persistent configuration data for each cluster member. With Grid Plug-and-Play, most of the cluster configuration for nodes is configured dynamically as nodes are added to the cluster, and the cluster is reconfigured when nodes are removed from the cluster.

Grid Naming Service (GNS)

Grid Naming Service enables the cluster to advertise hostnames and IP addresses dynamically as nodes are added and removed from the cluster, requiring minimal additional network address configuration in the DNS.

To use GNS, before grid infrastructure installation, you must configure your domain name server (DNS) to send to the GNS virtual IP address name resolution requests for the subdomain GNS serves. Refer to the grid infrastructure installation guide for DNS configuration requirements.

If you use GNS, then you need to specify a static IP address for the GNS VIP address, and delegate a subdomain to be forwarded to that static GNS IP address.

As nodes are added to the cluster, your organization's DHCP server can provide addresses for these addresses dynamically. These addresses are then registered automatically in GNS, and GNS provides resolution within the subdomain to cluster node addresses registered with GNS.

Cluster Name

In the Cluster Name field, provide a name for the cluster. The cluster name is used to identify member nodes of the cluster you create. The default value for cluster name is based on the local node name. If you change the cluster name from the default, then the cluster name that you use must be globally unique throughout your enterprise.

Cluster names must be at least one character long, and can be up to 15 characters in length. For example:

sales

SCAN Name

The single client access name (SCAN) is a hostname used to provide service access for clients to the cluster. Because the SCAN is associated with the cluster as a whole, rather than to a particular node, the SCAN makes it possible to add or remove nodes from the cluster without needing to reconfigure clients. It also adds location independence for the databases, so that client configuration does not have to depend on which nodes are running a particular database. Clients can continue to access the cluster in the same way as with previous releases, but Oracle recommends that clients accessing the cluster use the SCAN.

The SCAN should be configured so that it is resolvable either by using Grid Naming Service (GNS) within the cluster, or by using Domain Name Service (DNS) resolution. At a minimum, the SCAN name must resolve to at least one address. For high availability and scalability, Oracle recommends that you configure the SCAN name so that it resolves to three IP addresses.

For example, if the cluster name is sales, and you choose to use GNS, then the SCAN name is sales.local, and it is resolved to IP addresses allocated from the DHCP server.

SCAN Port

The default SCAN port for the SCAN virtual IP address is port 1521, but another port can be provided if that port is not available. Oracle Universal Installer verifies that the SCAN port provided is a valid port number, and is not used for any other purpose. After installation, a TNS listener listens to this port to respond to client connections to the SCAN name.

Example of GNS Configuration

The following table shows how the system is configured after installation if you select to configure Grid Naming Service (GNS):

^Footnote 1 Node host names may resolve to multiple addresses, including VIP addresses currently running on that host.

Example of Manual Configuration

The following table shows the addresses that might be configured for a two node cluster where you choose not to use GNS, where each node has one public and one private interface, and where you have defined a SCAN domain address to resolve on your DNS to one of three IP addresses:

^Footnote 1 Node host names may resolve to multiple addresses.

The addresses to which the SCAN resolves are assigned by Oracle Clusterware, so they are not fixed to a particular node. To enable VIP failover, the configuration shown in the preceding table defines the SCAN addresses and the public and VIP addresses of both nodes on the same subnet, 192.0.2.