1.3 How True Cache Works

At a high level, here's how Oracle True Cache works.

• An application decides whether to query data from True Cache or the primary database. For details on how this works, see Application Usage Models.
• True Cache satisfies queries by using data that's cached in its memory. When the data isn't in the cache, True Cache fetches the data from the primary database.
• True Cache is empty when it starts up, so it reads large chunks of data to populate the cache. After a block is cached, it's updated automatically through redo apply from the primary database. This is similar to the update mechanism used in Oracle Active Data Guard.
• A query to True Cache returns only committed data, and the data is always consistent.
• Like all caches, the True Cache data might not be the most current data as it exists in the primary database.
• If multiple True Caches exist and serve the same database application service, the listener automatically distributes and load balances sessions to each cache.