The two you mentioned: using RMAN for backup and MTS. It is not required, but is recommended if you are using either of the above. If you don't use it, memory for user sessions and RMAN backup is allocated from the shared pool, which in turn may cause fewer SQL statements to be cached.
Default size is zero. Minimum size is 600K. Max size is OS dependent, but will be at least 2GB.
As LARGE POOL don't uses LRU algorithm,
What should I be doing to avoid ORA-4031, will Oracle releases memory from LARGE POOL once the session dis connects.
How LARGE POOL space is released once the RMAN backup is over.
What should be the value LARGE_POOL_MIN_ALLOC, as I read somewhere, each active session needs around 300KB, should I set it close to this no.