how to check if db_big_table_cache_percent_target is being actively used

Hi,

I configured db_big_table_cache_percent_target=90 and am running PX queries.

however,  select * from gv$BT_SCAN_CACHE shows only zeros in  OBJECT_COUNT , MEMORY_BUF_ALLOC ,

all these columns in  V$BTS_STAT are zero as well :  DALLOC      DFREE     NALLOC      NFREE      DTIME     TALLOC      TFREE      TTIME       FLAG     CON_ID

How do i confirm that the big table cache is actually being used and how much of it is being used?

like breakup of shared_pool, is there a view which tells us how much of buffer cache is currently being used as big_table_cache?

Note : I did ensure that session is using autodop.