在oracle 10G或者11G版本中，如何合理设置shared pool大小，对oracle数据库的性能影响很大。
Shared Pool的大小设置规则如下：
1.查到shared pool设置的合理值，语句如下：
select ‘Shared Pool‘ component,
shared_pool_size_for_estimate estd_sp_size,
estd_lc_time_saved_factor parse_time_factor,
case
when current_parse_time_elapsed_s + adjustment_s < 0 THEN
0
ELSE
current_parse_time_elapsed_s + adjustment_s
END response_time
FROM (select shared_pool_size_for_estimate,
shared_pool_size_factor,
estd_lc_time_saved_factor,
a.estd_lc_time_saved,
e.VALUE / 100current_parse_time_elapsed_s,
c.estd_lc_time_saved - a.estd_lc_time_saved adjustment_s
from v$shared_pool_advice a,
(select * from v$sysstat where NAME = ‘parse time elapsed‘) e,
(select estd_lc_time_saved
from v$shared_pool_advice
where shared_pool_size_factor = 1) c);
2.设置上个SQL语句中查到的PARSE_TIME_FACTOR首次等于1的记录所在行的ESTD_SP_SIZE的值为shared pool。
3.设置语句如下：
alter system set shared_pool_size=XXX scope=spfile;或者alter system set shared_pool_size=XXX scope=both;