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Don Burleson Blog 







Understanding How CRS Manages the VIPs

Oracle Database Tips by Donald Burleson

VIPs are called ?Virtual IPs? because they are not permanently assigned to a given NIC on a given node. A VIP could be supported by an alternate node in the cluster. To demonstrate this, the crs_status script needs to be installed. Verify this with the command which crs_status. If it is not installed, turn to appendix B for instructions.

With the crs_statusscript installed, shut down both nodes. Next, start up only oracle1 and login immediately. Quickly launch a gnome-terminal, and repeatedly run the crs_status command. This will allow you to view the progression of the crs services as they start, as shown in Figure 8.10.

The vip is the first service to start. Client machines on the network are configured to find the listener at the vip address, so without it, crs will not start the listener.

After starting the vip, listener, gsd, and ons, oracle1 checks for the alternate node. With the alternate node absent, oracle1 starts the vip that is normally assigned to oracle2. Now, clients that are looking for a listener on oracle2 will find a node to connect to even though oracle2 is down.

Figure 8.11 demonstrates the use of the command /sbin/ifconfig | grep eth ?A1 to view a list of IPs supported by the node and which NICs support them.

Now, start up oracle2. Allow it a few minutes to start up. Use the crs_status command repeatedly from oracle1 to watch the services of oracle2 come online. First, the vip is taken offline on oracle1. Then it is put online on oracle2. Figure 8.12 demonstrates the progression.


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