SQL> SELECT name, sum(value/1024/1024) "Value - MB"
  2     FROM v$statname n, v$session s, v$sesstat t
  3    WHERE s.sid=t.sid
  4      AND n.statistic# = t.statistic#
  5      AND s.type = 'USER'
  6      AND s.username is not NULL
  7      AND n.name in ('session pga memory', 'session pga memory max',
  8          'session uga memory', 'session uga memory max')
  9    GROUP BY name;
 
NAME                                                             Value - MB
---------------------------------------------------------------- ----------
session uga memory                                               25,4581985
session uga memory max                                           42,1707000
session pga memory                                               40,7932128
session pga memory max                                           73,4807128
SQL> SELECT (
  2     (SELECT SUM(value) FROM V$SGA) -
  3     (SELECT CURRENT_SIZE FROM V$SGA_DYNAMIC_FREE_MEMORY)
  4     )/1024/1024 "SGA_TARGET"
  5  FROM DUAL;
 
SGA_TARGET
----------
      2048