SORT_AREA_SIZE and HASH_AREA_SIZE

Question

Guys,
Could someone explain the purpose of altering the SORT_AREA_SIZE and HASH_AREA_SIZE database parameters?
I had come across the following lines of code in one of my new application's package.
ALTER SESSION SET WORKAREA_SIZE_POLICY = MANUAL;
ALTER SESSION SET SORT_AREA_SIZE =xxx;
ALTER SESSION SET HASH_AREA_SIZE =yyy;
Thanks,
Bhagat

Answer 1

Thank you Sankar!
I've to perform ETL operation whereby it extracts data from a remote datasource,does sorting and loads into our database which involves huge amount of hash and sort.
So,I'm wondering how to dynamically set the value of either SORT_AREA_SIZE or HASH_AREA_SIZE or PGA_AGGREGATE_TARGET.Since our database is in 9i,I understand that adjusting the PGA_AGGREGATE_TARGET parameter would do the job for me.
I've read in an article that
The DBA may wish to consider dynamically changing the pga_aggregate_target parameter when any one of the following conditions are true:
Whenever the value of the v$sysstat statistic “estimated PGA memory for one-pass” exceeds pga_aggregate_target, the pga_aggregate_target should be increased.
==>How much should be the increase?
  1  select name,value
  2  from
  3  v$pgastat
  4  order by
  5* value desc
SQL> /
NAME                                                                  VALUE
bytes processed                                                  1.1742E+10
aggregate PGA target parameter                                    25165824
maximum PGA allocated                                              20128768
total PGA allocated                                                17669120
aggregate PGA auto target                                          12653568
total PGA inuse                                                    11108352
global memory bound                                                 1257472
maximum PGA used for auto workareas                                  688128
cache hit percentage                                                    100
total freeable PGA memory                                                 0
PGA memory freed back to OS                                               0
NAME                                                                  VALUE
maximum PGA used for manual workareas                                     0
over allocation count                                                     0
extra bytes read/written                                                  0
total PGA used for manual workareas                                       0
total PGA used for auto workareas                                         0
SQL> select name c1,cnt c2,decode(total, 0, 0, round(cnt*100/total)) c3
  2  from
  3  (
  4  select name,value cnt,(sum(value) over ()) total
  5  from
  6  v$sysstat
  7  where
  8  name like 'workarea exec%'
  9  );
Workarea
Profile                                    Count Percentage
workarea executions - optimal          1,098,557        ###
workarea executions - onepass                  0          0
workarea executions - multipass                0          0If I've an Oracle job which runs every minute or so to check the specified values and dynamically make adjustments to pga_aggregate_target,would it be the optimal way to go about?
Many Thanks !!!!
Regards,
Bhagat
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