RAC配置 VIP的作用
Why do we have a Virtual IP (VIP) in Oracle RAC 10g or 11g? Why
does it just return a dead connection when its primary node
fails?
The goal is application availability.
When a node fails, the VIP associated with it is automatically
failed over to some other node. When this occurs, the following
things happen.
(1) VIP detects public network failure which generates a FAN (Fast
Application Notification) event.
(2) the new node re-arps the world indicating a new MAC address for
the IP.
(3) connected clients subscribing to FAN immediately receive
ORA-3113 error or equivalent. Those not subscribing to FAN will
eventually time out.
(4) New connection requests rapidly traverse the tnsnames.ora
address list skipping over the dead nodes, instead of having to
wait on TCP-IP timeouts
Without using VIPs or FAN, clients connected to a node that died
will often wait for a TCP timeout period (which can be up to 10
min) before getting an error.
As a result, you don't really have a good HA solution without using
VIPs and FAN. The easiest way to use FAN is to use an integrated
client with Fast Connection Failover (FCF) such as JDBC, OCI, or
ODP.NET.
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