Associated Arrays...How are they managed?

Hi I have a question about how the associative arrays(table data structure in pl/sql) are managed by oracle. Does Oracle keep the data in memory and start paging it to disk once they reach a certain size or does it keep certain amount in memory and use some temporary table to which it insert and retrieve data as and when needed.
This is important to me as I feel that I may end up putting a lot of data in the associative arrays and I know for certain that paging is really slow.

Thanks for your insight..

Regards,
Sumit

Have you created a test case and run stats while doing so? This is an opinionated question as we are not privy to your os, configuration, oracle version, memory, application, etc.