The I/O buffer cache manages data pages. It makes a certain number of the pages available to the converter; it makes the other pages available to the data cache.
If the converter grows and requires more pages during database operation, the distribution of the pages between the converter and data cache is changed dynamically to meet this requirement.
When the database instance is started, the I/O buffer cache is created in the main memory in accordance with the size entered in the general database parameter CACHE_SIZE.