The database system uses the I/O buffer cache to manage all of the main memory that is available for I/O operations.
When the database instance starts, the database system assigns the I/O buffer cache the size specified in the general database parameter CACHE_SIZE.
The converter and the data cache are the most important main memory consumers that the database system manages in the I/O buffer cache. If the converter grows while the database is running, and requires more pages, the database system gives it more pages from the I/O buffer cache. If no more pages are available there, data is displaced from the data cache and made available to the converter.
See also:
Concepts of the Database System, General Database Parameters