Oracle RAC Interview Questions/FAQs Part2
21. Who will take backup of OCR files?
crsd will take backup.
22. What is split brain syndrome?
Will arise when two or more instances attempt to control a cluster database. In a two-node environment, one instance attempts to manage updates simultaneously while the other instance attempts to manage updates.
23. What are various IPs used in RAC? Or How may IPs we need in RAC?
Public IP, Private IP, Virtual IP, SCAN IP
24. What is the use of virtual IP?
When a node fails, the VIP associated with it is automatically failed over to some other node and new node re-arps the world indicating a new MAC address for the IP. Subsequent packets sent to the VIP go to the new node, which will send error RST packets back to the clients. This results in the clients getting errors immediately.
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.
25. What is the use of SCAN IP (SCAN name) and will it provide load balancing?
Single Client Access Name (SCAN) is a new Oracle Real Application Clusters (RAC) 11g Release 2, feature that provides a single name for clients to access an Oracle Database running in a cluster. The benefit is clients using SCAN do not need to change if you add or remove nodes in the cluster.
26. How many SCAN listeners will be running?
Three SCAN listeners only.
27. What is FAN?
Applications can use Fast Application Notification (FAN) to enable rapid failure detection, balancing of connection pools after failures, and re-balancing of connection pools when failed components are repaired. The FAN process uses system events that Oracle publishes when cluster servers become unreachable or if network interfaces fail.
28. What is FCF?
Fast Connection Failover provides high availability to FAN integrated clients, such as clients that use JDBC, OCI, or ODP.NET. If you configure the client to use fast connection failover, then the client automatically subscribes to FAN events and can react to database UP and DOWN events. In response, Oracle gives the client a connection to an active instance that provides the requested database service.
29. What is TAF and TAF policies?
Transparent Application Failover (TAF) - A runtime failover for high availability environments, such as Real Application Clusters and Oracle Real Application Clusters Guard, TAF refers to the failover and re-establishment of application-to-service connections. It enables client applications to automatically reconnect to the database if the connection fails, and optionally resume a SELECT statement that was in progress. This reconnect happens automatically from within the Oracle Call Interface (OCI) library.
30. How will you upgrade RAC database?
31. What are rolling patches and how to apply?
32. How to add/remove a node?
33. What are nodeapps?
VIP, listener, ONS, GSD
34. What is gsd (Global Service Daemon)?
35. How to do load balancing in RAC?
36. What are the uses of services? How to find out the services in cluster?
Applications should use the services to connect to the Oracle database. Services define rules and characteristics (unique name, workload balancing, failover options, and high availability) to control how users and applications connect to database instances.
37. How to find out the nodes in cluster (or) how to find out the master node?
# olsnodes -- Which ever displayed first, is the master node of the cluster.
select MASTER_NODE from v$ges_resource;
To find out which is the master node, you can see ocssd.log file and search for "master node number".
38. How to know the public IPs, private IPs, VIPs in RAC?
# olsnodes -n -p -i
node1-pub 1 node1-prv node1-vip
node2-pub 2 node2-prv node2-vip
39. What utility is used to start DB/instance?
srvctl start database –d database_name
srvctl start instance –d database_name –i instance_name
40. How can you shutdown single instance?
srvctl stop instance –d database_name –i instance_name