Use the PGA Advisor

可以通过视图或者AWR，查看到PGA的建议。
 
SQL> select * from V$PGA_TARGET_ADVICE;
 
PGA_TARGET_FOR_ESTIMATE FACTOR STATUS BYTES_PROCESSED ESTD_EXTRA_BYTES_RW HIT_PERCENTAGE ESTD_OVERALLOC_COUNT
----------------------- ------ ------ --------------- ------------------- -------------- --------------------
               13107200  0.125 ON           125043712            15679488             89                    3
               26214400   0.25 ON           125043712            15679488             89                    3
               52428800    0.5 ON           125043712                   0            100                    0
               78643200   0.75 ON           125043712                   0            100                    0
              104857600      1 ON           125043712                   0            100                    0
              125829120    1.2 ON           125043712                   0            100                    0
              146800640    1.4 ON           125043712                   0            100                    0
              167772160    1.6 ON           125043712                   0            100                    0
              188743680    1.8 ON           125043712                   0            100                    0
              209715200      2 ON           125043712                   0            100                    0
              314572800      3 ON           125043712                   0            100                    0
              419430400      4 ON           125043712                   0            100                    0
              629145600      6 ON           125043712                   0            100                    0
              838860800      8 ON           125043712                   0            100                    0
 
相关的视图还有：
select * from V$PGASTAT;
select * from DBA_HIST_PGASTAT;
select * from DBA_HIST_PGA_TARGET_ADVICE;
 
此外还可以通过EM的图形化界面查看memory advisor。