ORACLE优化查询资源消耗的语句

1> SQL ordered by Getsselect * from           (select substr(sql_text,1,40) sql,   buffer_gets,executions, buffer_gets/executions "Gets/Exec",             hash_value,address          from v$sqlarea                  where  buffer_gets > 0 and executions>0          order by buffer_gets desc)           where rownum <= 10 ; 2> SQL ordered by Readsselect * from                   (select substr(sql_text,1,40) sql,      disk_reads,executions, disk_reads/executions "Reads/Exec",                   hash_value,address                 from v$sqlarea    where disk_reads > 0 and executions >0                   order by disk_reads desc) where rownum <= 10; 3> SQL ordered by Executions select * from                     (select substr(sql_text,1,40) sql,      executions, rows_processed, rows_processed/executions "Rows/Exec",                  hash_value,address                  from v$sqlarea    where executions > 0               order by executions desc) where rownum <= 10 ; 4> SQL ordered by Parse Callsselect * from                    (select substr(sql_text,1,40) sql,      parse_calls,executions, hash_value,address                   from v$sqlarea    where parse_calls > 0              order by parse_calls desc) where rownum <= 10 ; 5> Running Time top 10 sqlselect * from              (select t.sql_fulltext,               (t.last_active_time-to_date(t.first_load_time,'yyyy-mm-dd hh24:mi:ss'))*24*60,              disk_reads,buffer_gets,rows_processed,                   t.last_active_time,t.last_load_time,t.first_load_time              from v$sqlarea t order by t.first_load_time desc)                   where rownum < 10;