Oracle Real Application Clusters (Oracle RAC) provides an excellent solution for improving query throughput. If you can get good performance from Oracle Text with a light query load, then you can expect to get excellent scalability from Oracle RAC as the query load increases.
Further improvements in Oracle Text performance in an Oracle RAC environment may be achieved by physically partitioning the text data and text indexes (using local partitioned indexes), and ensuring that partitions are handled by separate Oracle RAC nodes. This way, you avoid duplication of the cache contents across multiple nodes and, therefore, maximize the benefit of Oracle RAC cache fusion.
In Oracle 10g Release 1, each Oracle Text index partition must be forced into a separate database file when the index is created. This enables the use of the "re-mastering" feature in Oracle RAC to force database file affinity, in which each node concentrates on a particular database file and, therefore, a particular Oracle Text index partition.
In Oracle 10g Release 2 and forward, Oracle supports database object-level affinity, which makes it much easier to allocate index objects ($I and $R tables) to particular nodes.
While Oracle RAC offers solutions for improving query throughput and performance, is not a "magic bullet," and it will not necessarily enable you to continue to get the same performance improvements as you scale up the data volumes. You are more likely to see improvements by increasing the amounts of memory available to the SGA cache, or by partitioning your data in such a way that queries will normally not need to hit all of the partitions of a table in order to provide the required set of query results.