Oracle 12C: Full Database Caching

This feature is available starting with Oracle Database 12c Release 1 (12.1.0.2)
When to use it:

• when you have enough memory to keep all segments in memory
• when you are limited by I/O system and response time

Full database caching can be used to cache the entire database in memory. It should be used when
the buffer cache size of the database instance is greater than the entire database size. In Oracle RAC
systems this feature can be used when the combined buffer caches of all instances, with some extra
space to handle duplicate cached blocks between instances, is greater than the database size.
Caching the entire database provides significant performance benefits, especially for workloads that
were previously limited by I/O throughput or response time. More specifically, this feature
improves the performance of full table scans by forcing all tables to be cached.
Command to force full database caching:
SQL> startup mount
Oracle instance started.
Database mounted.
SQL> alter database force full database caching;
Database altered.
SQL> alter database open;
Database altered.
SQL> select force_full_db_caching from v$database;
FOR
—
YES