|
One of the key drivers to move to Oracle RAC is its compelling active/active architecture. This architecture improves high availability and provides better resource utilization. It reduces unplanned as well as planned downtime, but even if no problem occurs, Oracle RAC allows customers to distribute the workload to as many nodes as are available.
With a single SMP server, if anything fails the whole machine goes down – user processing is interrupted and can take 20 to 30 minutes to resume on a cold standby system (active/passive architecture). In such an environment, when the primary system fails, administrators have to manually dismount and remount storage volumes, user connections have to be established to the new server and the buffer cache in the standby's memory needs to be populated with the most frequently used data.
Oracle RAC's active/active system offers virtually uninterrupted processing for users and eliminates the need for these recovery steps – all cluster nodes are always connected to all the storage so no volume dismounting and remounting is required. Users on the surviving nodes remain connected, only the users on the failed node need to reconnect.
Oracle RAC helps to reduce planned downtime as well. As RAC nodes can be added and removed "on the fly," maintenance tasks such as hardware or operating system upgrades can be performed on individual nodes without shutting down the system completely.
|
