Test in probably 8i: SQL> select statistic#, name from v$statname where name like '%pga%' or name like '%uga%'; STATISTIC# NAME ---------- ---------------------------------------------------------------- 15 session uga memory 16 session uga memory max 20 session pga memory 21 session pga memory max SQL> select * from v$sesstat where statistic# in (15,16,20,21) and sid = 15; SID STATISTIC# VALUE ---------- ---------- ---------- 15 15 77004 15 16 77004 15 20 243208 15 21 243208 declare type array is table of varchar2(10) index by binary_integer; data array; begin data(1) := 'A'; end; / SQL> select * from v$sesstat where statistic# in (15,16,20,21) and sid = 15; SID STATISTIC# VALUE ---------- ---------- ---------- 15 15 77004 15 16 77004 15 20 243208 15 21 308744 <-- pga max (i.e. high water mark) increased declare type array is table of varchar2(32767) index by binary_integer; data array; begin for i in 1..1000000 loop data(i) := 'A'; end loop; end; / SQL> select * from v$sesstat where statistic# in (15,16,20,21) and sid = 15; SID STATISTIC# VALUE ---------- ---------- ---------- 15 15 77004 15 16 77004 15 20 1656612 <-- pga increased 15 21 1722148 <-- pga max increased declare type array is table of varchar2(32767) index by binary_integer; data array; begin for i in 1..1000000 loop data(i) := '12345678901234567890123456789012345678901234567890'; end loop; end; / SQL> select * from v$sesstat where statistic# in (15,16,20,21) and sid = 15; SID STATISTIC# VALUE ---------- ---------- ---------- 15 15 77004 15 16 77004 15 20 91534200 <-- pga increased 15 21 91599736 <-- pga max increased SQL> exec dbms_session.free_unused_user_memory PL/SQL procedure successfully completed. SQL> select * from v$sesstat where statistic# in (15,16,20,21) and sid = 15; SID STATISTIC# VALUE ---------- ---------- ---------- 15 15 77004 15 16 77004 15 20 251720 <-- down to almost the beginning value 15 21 91861880 <-- HWM stays of course SQL> select pga_used_mem,pga_alloc_mem,pga_freeable_mem,pga_max_mem from v$process where addr = '53E0B7B8'; PGA_USED_MEM PGA_ALLOC_MEM PGA_FREEABLE_MEM PGA_MAX_MEM ------------ ------------- ---------------- ----------- 209901 528181 0 91876197