In-memory Parallel Execution

In-memory parallel execution is another new feature introduced in Oracle Database 11g Release 2. This enhancement is another way that Oracle combines the benefits of parallel execution with a RAC environment.

When a RAC database executes a statement with parallel processes, the database checks to see if the objects referenced by the statement could be cached in the aggregated data buffers across all nodes in the server. (This decision is based on a set of heuristics, rather than a simple size calculation.) If there is enough cache available, the granules created for parallel execution are stored in memory on separate nodes, and all operations on those granules are executed on those nodes. This arrangement delivers the benefits of caching entire objects in memory without needing to have the entire amount of memory on a single node.