Oracle Real Application Clusters (RAC) is an option for Oracle Databases. It is a cluster database with a shared cache architecture that increases scalability and availability. Oracle RAC support is included in the Oracle Database Standard Edition and is an extra cost option for Enterprise Edition.
I did some Googling and couldn't find an answer to this question more recent than a few years ago, so I thought I'd ask. Oracle's RAC feature offers load-balancing for both read and write ...