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请问关于Oracle 11G R2中的SCAN该如何理解?
看了下面的解释更迷惑了。我在做Oracle 11G R2 RAC测试时,将SCAN指定为了一台实际存在的机器IP,结果造成Installer失败。不理解SCAN究竟是做什么用的。
请各位指教。
Understanding SCAN Addresses and Client Service Connections
Public network addresses are used to provide services to clients. If your clients are connecting to the Single Client Access Name addresses, then you may need to change public and virtual IP addresses as you add or remove nodes from the cluster, but you do not need to update clients with new cluster addresses.
SCANs function like a cluster alias. However, SCANs are resolved on any node in the cluster, so unlike a VIP address for a node, clients connecting to the SCAN no longer require updated VIP addresses as nodes are added to or removed from the cluster. Because the SCAN addresses resolve to the cluster, rather than to a node address in the cluster, nodes can be added to or removed from the cluster without affecting the SCAN address configuration.
The SCAN is a fully qualified name (host name+domain) that is configured to resolve to all the addresses allocated for the SCAN. The addresses resolve using Round Robin DNS either on the DNS server, or within the cluster in a GNS configuration. SCAN listeners can run on any node in the cluster. SCANs provide location independence for the databases, so that client configuration does not have to depend on which nodes run a particular database.
Oracle Database 11g release 2 (11.2) and later instances only register with SCAN listeners as remote listeners. Upgraded databases register with SCAN listeners as remote listeners, and also continue to register with all node listeners.
The Single Client Access Name (SCAN) should really be defined in the DNS or GNS and round-robin between one of 3 addresses, which are on the same subnet as the public and virtual IPs. In this article I've defined it as a single IP address in the "/etc/hosts" file, which is wrong and will cause the cluster verification to fail, but it allows me to complete the install.
The Single Client Access Name (SCAN) should really be defined in the DNS or GNS and round-robin between one of 3 addresses, which are on the same subnet as the public and virtual IPs. In this article I've defined it as a single IP address in the "/etc/hosts" file, which is wrong and will cause the cluster verification to fail, but it allows me to complete the install. |
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