12c Server Pools in action : Instance and service failover to server pools

In the Previous post we have converted the orcl database to server pool OLTP_SP which is running on three nodes rac01,rac03,rac04 and free server is available in rac02.

Okay lets have some discussion before proceeding,

1. Does in pre 11g version , if a instance crashed does it failed over to any node?

No. Because there is no free node available, and Instances will run on all nodes, and bound to start on specific node. Means there is no instance failover instead service will failover to available node.

Keeping in mind, with server pools we have flexibility in failing over the instances along with it services if we keep our databases in policy managed where oracle grid infrastructure will make your instances running on the serverpool it defined. That's is the reason when you define the database to a server pool (like below) you just specify the server pool name only rather how many instances etc etc.

Ex: srvctl modify database –d orcl –g OLTP_SP

note: OLTP_SP is a server pool with 3 nodes runnings, so now although i have four nodes my database will have only running 3 instances in three nodes.

Read on now,

If we kill a pmon or crash the node rac01, the free pool node rac02 will be assigned to server pool OLTP_SP, lets see in action.

Configuration check,

(BTW, Many Thanks Deepak (again) for sending this wonderful screenshots)

Lets kill the pmon in rac01,

Now monitor the server pool and the read  the comments updated in the screenshots.

As above the pmon has been killed, now orcl_4 is not running rac01, initially the free pool has 1 server and after a while the free pool has given away 1 server  (as you can see 0 at last) to server pool , and finally you can see the three instances are back, but this time it is rac02,rac03,rac04.

As we have seen the instance crash is failing over its instance to free pool, Next Post lets see Service failover with in server pools

Thanks for reading,

Geek DBAGeek DBA