Total System Global Area 1034907984 bytes
Fixed Size                   737616 bytes
Variable Size             385875968 bytes
Database Buffers          637534208 bytes
Redo Buffers               10760192 bytes

show parameter db_cache

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_cache_size                        big integer 637534208

SQL> l
  1  select 'V$BUFFER_POOL_STATISTICS' object, PHYSICAL_READS,DB_BLOCK_GETS, CONSISTENT_GETS
  2  from V$BUFFER_POOL_STATISTICS
  3  union all
  4  select 'v$SYSSTAT' object, pr.value ,   bg.value , cg.value
  5  from    v$sysstat pr,   v$sysstat bg,   v$sysstat cg
  6* where    pr.name='physical reads' and   bg.name='db block gets'  and   cg.name ='consistent gets'
SQL> /

OBJECT                   PHYSICAL_READS DB_BLOCK_GETS CONSISTENT_GETS
------------------------ -------------- ------------- ---------------
V$BUFFER_POOL_STATISTICS       37218794      69984093        94587588
v$SYSSTAT                      84233788      69984101        94587642

SQL>Select * from V$sgastat
Where name='free memory'
and pool='shared pool';

COLUMN size_for_estimate FORMAT 999,999,999,999 HEADING 'Cache Size (MB)'
COLUMN buffers_for_estimate FORMAT 999,999,999 HEADING 'Buffers'
COLUMN estd_physical_read_factor FORMAT 999.90 HEADING 'Estd Phys|Read Factor'
COLUMN estd_physical_reads FORMAT 999,999,999 HEADING 'Estd Phys| Reads'
SELECT size_for_estimate, buffers_for_estimate,
       estd_physical_read_factor, estd_physical_reads
  FROM v$db_cache_advice
  WHERE name          = 'DEFAULT'
  AND block_size    = (SELECT value FROM v$parameter 
  WHERE name = 'db_block_size')
  AND advice_status = 'ON';

SELECT name, block_size, size_for_estimate, size_factor,
       estd_physical_reads
FROM v$db_cache_advice;