sql monitroing

在sql调优中，对于sql语句的实时监控显得尤为重要，如果某条sql语句的性能比较差。可能从前端的直观感觉就是执行时间比较长。
对于dba来说，可能关注的相关因素需要多一些.
1）可以通过top命令来监控sql的性能情况，查看cpu使用率较高的oracle process,然后通过查看session和process得绑定得到对应的session,然后得到对应的sql语句。
2) 如果已经过去了一段时间，而且在缓存中已经没有对应的sql语句了，可以通过awr得到一个大体的报告做分析，排查问题的大体范围，在这个基础上定位更精准的时间段，做一个ash。
3) 如果已经定位到sql_id了，想做进一步的分析，可以通过awrsqrpt来得到对应时间段的执行计划
。。。
对于执行计划的分析方式就更多了，但是oracle也提供了一些比较方便的功能集，你用或者不用，它就在那里。
sql monitor是一个实时的sql监控工具，11g里对dbms_tune做了不少的改进和提升。动态视图v$sql_monitor中有被监控的sql语句的一些明细信息。
一般对于执行时间超过5秒的sql语句，都会成为监控对象。
首先看看11g的库是否启用了这项功能

SQL> show parameter CONTROL_MANAGEMENT_PACK_ACCESS;
control_management_pack_access string DIAGNOSTIC+TUNING

然后模拟一个大查询，做个并行，表t里面有150万左右的数据，我本地的机器查询奎尼丁超过5秒。

SQL> select /*+ parallel(8) */count(1) from t ;
1536604

然后查看v$sql_minotor
set long 99999
set pages 0
set linesize 200
col status format a20
col username format a30
col module format a20
col program format a20
col sql_id format a20
col sql_text format a50
select STATUS , USERNAME , MODULE , PROGRAM, SQL_ID , SQL_TEXT from v$sql_monitor
/
DONE (ALL ROWS) 21df1v060g0wq
DONE (ALL ROWS) 21df1v060g0wq
DONE (ALL ROWS) 21df1v060g0wq
DONE (ALL ROWS) 21df1v060g0wq
DONE (ALL ROWS) N1 SQL*Plus sqlplus@rac1 (TNS V1 21df1v060g0wq select /*+ parallel(8) */count(1) from t
-V3)
DONE (ALL ROWS) 21df1v060g0wq
DONE (ALL ROWS) 21df1v060g0wq
DONE (ALL ROWS) 21df1v060g0wq
DONE (ALL ROWS) 21df1v060g0wq

9 rows selected.

下面这个功能才是重点，生成报告。
这个报告风格类似awr,ash有html,text,xml的格式类型。输入sql_id就能得到具体的报告。
col comm format a200
SELECT dbms_sqltune.report_sql_monitor(
sql_id => '21df1v060g0wq',
report_level => 'ALL',
type=>'TEXT'
) comm
FROM dual;

展示一个文本格式的报告。
SQL Text
------------------------------
select /*+ parallel(8) */count(1) from t

Global Information
------------------------------
Status : DONE (ALL ROWS)
Instance ID : 1
Session : N1 (254:77)
SQL ID : 21df1v060g0wq
SQL Execution ID : 16777216
Execution Started : 07/10/2014 06:40:49
First Refresh Time : 07/10/2014 06:40:52
Last Refresh Time : 07/10/2014 06:41:06
Duration : 17s
Module/Action : SQL*Plus/-
Service : SYS$USERS
Program : sqlplus@rac1 (TNS V1-V3)
Fetch Calls : 1

Global Stats
=========================================================================================
| Elapsed | Cpu | IO | Concurrency | Other | Fetch | Buffer | Read | Read |
| Time(s) | Time(s) | Waits(s) | Waits(s) | Waits(s) | Calls | Gets | Reqs | Bytes |
=========================================================================================
| 114 | 1.81 | 108 | 2.67 | 1.14 | 1 | 8913 | 1193 | 68MB |
=========================================================================================

Parallel Execution Details (DOP=8 , Servers Allocated=8)
============================================================================================================================================
| Name | Type | Server# | Elapsed | Cpu | IO | Concurrency | Other | Buffer | Read | Read | Wait Events |
| | | | Time(s) | Time(s) | Waits(s) | Waits(s) | Waits(s) | Gets | Reqs | Bytes | (sample #) |
============================================================================================================================================
| PX Coordinator | QC | | 3.10 | 0.04 | 0.01 | 2.67 | 0.38 | 5 | 1 | 8192 | os thread startup (3) |
| p000 | Set 1 | 1 | 14 | 0.21 | 14 | | | 1075 | 143 | 8MB | direct path read (13) |
| p001 | Set 1 | 2 | 14 | 0.23 | 13 | | 0.22 | 1190 | 158 | 9MB | direct path read (12) |
| p002 | Set 1 | 3 | 14 | 0.21 | 14 | | | 1078 | 142 | 8MB | direct path read (12) |
| p003 | Set 1 | 4 | 14 | 0.20 | 14 | | | 1030 | 139 | 8MB | direct path read (14) |
| p004 | Set 1 | 5 | 14 | 0.25 | 13 | | 0.07 | 1166 | 156 | 9MB | direct path read (13) |
| p005 | Set 1 | 6 | 14 | 0.22 | 13 | | 0.23 | 1074 | 145 | 8MB | direct path read (13) |
| p006 | Set 1 | 7 | 14 | 0.25 | 14 | | | 1288 | 176 | 10MB | direct path read (14) |
| p007 | Set 1 | 8 | 14 | 0.20 | 14 | | 0.23 | 1007 | 133 | 8MB | direct path read (13) |
============================================================================================================================================

SQL Plan Monitoring Details (Plan Hash Value=3126468333)
========================================================================================================================================================
| Id | Operation | Name | Rows | Cost | Time | Start | Execs | Rows | Read | Read | Activity | Activity Detail |
| | | | (Estim) | | Active(s) | Active | | (Actual) | Reqs | Bytes | (%) | (# samples) |
========================================================================================================================================================
| 0 | SELECT STATEMENT | | | | 1 | +17 | 1 | 1 | | | | |
| 1 | SORT AGGREGATE | | 1 | | 1 | +17 | 1 | 1 | | | | |
| 2 | PX COORDINATOR | | | | 17 | +1 | 9 | 8 | | | 2.63 | os thread startup (3) |
| 3 | PX SEND QC (RANDOM) | :TQ10000 | 1 | | 1 | +17 | 8 | 8 | | | | |
| 4 | SORT AGGREGATE | | 1 | | 14 | +4 | 8 | 8 | | | 0.88 | Cpu (1) |
| 5 | PX BLOCK ITERATOR | | 2M | 338 | 13 | +5 | 8 | 2M | | | | |
| 6 | TABLE ACCESS FULL | T | 2M | 338 | 14 | +4 | 115 | 2M | 1192 | 68MB | 96.49 | Cpu (6) |
| | | | | | | | | | | | | direct path read (104) |
========================================================================================================================================================

文本格式的报告简单明了，但是html的报告来说更加清晰，而且还有额外的一些信息。性能瓶颈类问题，一目了然。