In the absence of visualization tools to monitor database performance, common scripts come in handy. Here are a few scripts related to Oracle Performance for your reference. The following scripts have passed the Oracle 10g test, and Oracle 11g may need to be adjusted accordingly.

1. Find SQL statements with the most buffer \

--filename: top_sql_by_buffer_gets.sql
--Identify heavy SQL (Get the SQL with heavy BUFFER_GETS)
SET LINESIZE 190
COL sql_text FORMAT a100 WRAP
SET PAGESIZE 100

SELECT *
  FROM (  SELECT sql_text,
                 sql_id,
                 executions,
                 disk_reads,
                 buffer_gets
            FROM v$sqlarea
           WHERE DECODE (executions, 0, buffer_gets, buffer_gets / executions) >
                    (SELECT AVG (DECODE (executions, 0, buffer_gets, buffer_gets / executions))
                            + STDDEV (DECODE (executions, 0, buffer_gets, buffer_gets / executions))
                       FROM v$sqlarea)
                 AND parsing_user_id != 3D
        ORDER BY 4 DESC) x
 WHERE ROWNUM <= 10;

2. Find SQL statements with the most disk? Reads overhead

--filename:top_sql_disk_reads.sql
--Identify heavy SQL (Get the SQL with heavy DISK_READS)
SET LINESIZE 190
COL sql_text FORMAT a100 WRAP
SET PAGESIZE 100

SELECT *
  FROM (  SELECT sql_text,
                 sql_id,
                 executions,
                 disk_reads,
                 buffer_gets
            FROM v$sqlarea
           WHERE DECODE (executions, 0, disk_reads, disk_reads / executions) >
                    (SELECT AVG (DECODE (executions, 0, disk_reads, disk_reads / executions))
                            + STDDEV (DECODE (executions, 0, disk_reads, disk_reads / executions))
                       FROM v$sqlarea)
                 AND parsing_user_id != 3D
        ORDER BY 3 DESC) x
 WHERE ROWNUM <= 10

3. Look for events that have caused excessive resource overhead in the last 30 minutes

--filename:top_event_in_30_min.sql
--Last 30 minutes result those resources that are in high demand on your system.
SET LINESIZE 180
COL event FORMAT a60
COL total_wait_time FORMAT 999999999999999999

  SELECT active_session_history.event,
         SUM (
            active_session_history.wait_time
            + active_session_history.time_waited)
            total_wait_time
    FROM v$active_session_history active_session_history
   WHERE active_session_history.sample_time BETWEEN SYSDATE - 60 / 2880
                                                AND SYSDATE
         AND active_session_history.event IS NOT NULL
GROUP BY active_session_history.event
ORDER BY 2 DESC;