Questions from the Expert Panel at IOUG

The Oracle RAC SIG (www.oracleracsig.org) held an expert panel at their recent Collaborate 08 conference in Denver. Here are the questions (along with the answers)

1. Do you support Virtualization - Today Oracle RAC is supported on most hardware virtualization offering such as IBM LPAR, HP VPAR, SUN GLOBAL CONTAINERS, SUN E25K Partitions. Check certify on Oracle Metalink for details. Today Oracle RAC is not certified on any software virtualization such as VMWARE or Oracle VM.
   
2. How large a cluster can I have? Oracle RAC supports up to 100 instances and Oracle Clusterware supports up to 100 nodes in a cluster. How many nodes you implement depends on your requirements for the cluster. Remember if I only have 2 nodes in the cluster, I lose 1, I have lost 50% of my processing power and 50% of my users will be affected. If I have a 4 node cluster, I loase a node, I will only affect 25% of my users and have lost only 25% of my processing power. Scalability of the application depends on how well written the application is (as in all situations!). Many customers today run in 4, 8, 16 or more nodes.
   
3. Should I consolidate multiple applications in a cluster? Yes, cluster consolidation is a great way to get started on the grid and share resources amoung apps. It is easy to adjust the number of instances running for a given application within the cluster. Many customers take advantage of this method today.
   
4. How do I upgrade from 9i RAC to Oracle RAC 10g? There are many options open for upgrade depending on how long an outage you can take and how big your database is. Check the Oracle documentation for details. There is also a new upgrade companion available in Metalink. If you would like to remove 3rd party clusterware from the system, you should completely de-install before installing Oracle Clusterware.
   
5. How much traffic on the interconnect is Oracle Clusterware vs Oracle RAC? Oracle Clusterware sends small messages so it is a fairly small bandwidth user. Oracle RAC usage depends on the application and how much data is shared between SGAs. Depending on the blocksize of your database, the database transfered is messages as well as data blocks.
   
6. Should I use connection load balancing, what should be set up? In an Oracle RAC environment, yes you should use SQL*NET connection load balancing. If you use DBCA to create your database, it will set it up for you. This will load balance the client connections across the instances that are currently running the service. If you want better load balancing and fast failover of connections, have a look at the OTN whitepaper linked below

http://www.oracle.com/technology/products/database/clustering/pdf/awmrac11g.pdf