第一章： 调优综述
1、调优的问题
应用软件： 设计阶段、开发阶段、测试阶段、上线
1） 谁来调优
应用设计师：
应用逻辑性及应用的扩展性，数据库应用的架构(物理存储、逻辑存储、对象的架构）
开发人员： 编写高效的sql 代码
数据库管理员：
负责调整数据库的参数，参与测试，配合开发人员对测试中出现的问题加以解决
系统管理员：调整操作系统的参数（关于内存、I/O、交换分区等）
2）为什么调优
为应用上线后有一个良好的运行环境
3） 调优的目标
调优的目标必须量化（不是越快越好）
设定一个量化的目标（比如查询时间缩短到1min以内），达到目标后停止。
2、调优的过程
1）应用的设计和开发阶段
2）数据库配置阶段：
表空间及数据文件存储架构、表结构、索引等
3）新的应用上线
4）应用上线后故障排除和性能调整
3、调优的目标
1）减少和消除等待事件
2）使用最少的块来访问（索引、索引组织表、簇、使用大尺寸块、物化视图、避免行迁移和行链接等、建立分区表）
3）将数据块放入内存中访问
4）缩短响应时间
5）调整磁盘I/O
6）数据装载速度load（数据迁移）（并行、direct、nologgin）
7）减少恢复时间（recovery，调整备份周期）
4、需要调优的问题
1）会话没有被释放
2）游标设计问题
3）表关联的设计--表设计遵循范式，减少表里面记录的冗余；如果进行一些反常规的设计，可以减少表与表连接所消耗的资源。
5、调优的步骤
1）通过工具找出应用的瓶颈（操作系统：top、vmstat、iostat、topas、glance
；database：EM、statspack、awr、rda、oracle的动态性能视图）
2）分析、判断造成瓶颈的原因
3）设定一个量化的目标，进行解决
4）检查问题是否解决，如果没有达到目标，继续第三步。达到目标就结束。
6、调优和数据库安全
1）控制文件多元化（控制文件如果太多，会增加对磁盘的I/O,两个或三个就可以）
2）日志组成员的多元化（每个日志组两个成员分别放到不同的磁盘上）
3）频繁生成检查点（频繁的检查点会增加磁盘的I/O)
4)
数据文件备份（设计好的备份计划，使用增量备份）
5）启动归档（归档进程数、存放归档日志的磁盘I/O）
6) 数据块检查
10:40:51 SYS@ test1>show parameter check
NAME TYPE
VALUE
------------------------------------ -----------
------------------------------
db_block_checking string
FALSE
db_block_checksum string TRUE
7）当前并发的用户和事务的数量
第二章： 诊断和调优的工具
1、告警日志
11:54:28 SYS@ test1>show parameter dump
NAME TYPE
VALUE
------------------------------------ -----------
------------------------------
background_core_dump string
partial
background_dump_dest string
/u01/app/oracle/admin/test1/bd
ump
----告警日志
* 告警日志内容
* 启动时间以及操作模式的启动和关闭命令。
* 涉及物理结构的操作，使用ALTER DATABASE命令。
* 表空间操作。
*
所有日志切换与归档，包括所影响文件的名称。
* 用于启动实例的非默认初始化参数，还包括ALTER SYSTEM命令修改这些参数。
*
告警日志包含了影响数据库结构和实例的各种操作的连续历史记录。
* 告警日志不包含sql语句(DML,DDL)。
*
告警日志包含常见的告警与错误：
* 检查点不完全：说明日志文件过小而引起日志切换频繁。
* 无法打开文件：在数据库启动过程中产生。
*
块讹误：某个数据文件损坏引起。与DBA_EXTENTS视图一起查看。
* 归档存在问题：归档目的地满和不可用。
* 死锁。
----通过外部表方式管理告警日志
1)创建目录并授权
12:05:40 SYS@ test1>create
directory bdump as ‘/u01/app/oracle/admin/test1/bdump‘;
12:07:08 SYS@
test1>grant read ,write on directory bdump to public;
Grant succeeded.
2）创建外部表
sql >create table alert_log( text
varchar2(4000) )
organization external
(type oracle_loader
default
directory bdump
access parameters (records delimited by newline)
location(‘alert_test1.log‘))
REJECT LIMIT UNLIMITED;
3)查询
12:12:05 SYS@ test1>select * from alert_log where text like ‘%ORA-%‘;
----告警日志备份脚本
#!/bin/bash
cd
$ORACLE_BASE/admin/$ORACLE_SID/bdump
mkdir -p
bak
lg=alert_$ORACLE_SID.log
cat $lg| gzip -9c > bak/$lg.bak.`date
+%y%m%d`.gz && cat /dev/null > $lg
Oracle 11g:
#!/bin/bash
db_name=test1
cd
$ORACLE_BASE/diag/rdbms/$db_name/$ORACLE_SID/trace
mkdir -p
bak
lg=alert_$ORACLE_SID.log
cat $lg| gzip -9c > bak/$lg.bak.`date
+%y%m%d`.gz && cat /dev/null > $lg
2、后台进程trace 文件
记录后台进程日志信息，一般是后台进程的一些错误信息，不包含调优的信息
3、用户进程trace文件
-----用于统计用户执行的sql语句，可以通过这些统计信息，判断sql语句的执行过程和对资源调用
12:58:09 SYS@ test1>show parameter sql_trace
NAME TYPE
VALUE
------------------------------------ -----------
------------------------------
sql_trace boolean
FALSE
-------默认，oracle对用户执行的sql 语句不做跟踪
1）启用跟踪（对所有session的会话进行跟踪，一般比较少用）
13:01:55 SYS@ test1>alter system set sql_trace=true;
System altered.
Elapsed: 00:00:00.19
13:03:02 SYS@ test1>show parameter sql_trace
NAME TYPE
VALUE
------------------------------------ -----------
------------------------------
sql_trace boolean
TRUE
2）对当前用户的会话进行trace
13:06:23 SYS@ test1>alter session set
sql_trace=true;
Session altered.
---普通用户启用会话跟踪
13:07:45 SYS@ test1>grant alter session to public;
Grant succeeded.
Elapsed: 00:00:00.11
13:07:55 SYS@ test1>conn
scott/tiger
Connected.
13:07:59 SCOTT@ test1>alter session set
sql_trace =true;
Session altered.
Elapsed: 00:00:00.08
13:08:14 SCOTT@ test1>
案例：
13:07:59 SCOTT@ test1>alter session set sql_trace =true;
Session altered.
Elapsed: 00:00:00.08
13:08:14 SCOTT@ test1>analyze table emp compute
statistics;
Table analyzed.
Elapsed: 00:00:00.57
13:09:20 SCOTT@ test1>select ename,sal,deptno from
emp where deptno=10;
ENAME SAL DEPTNO
---------- ---------- ----------
CLARK
2450 10
KING 5000 10
MILLER
1300 10
Elapsed: 00:00:00.04
13:09:45 SCOTT@ test1>select ename,sal,deptno from
emp where deptno=20;
ENAME SAL DEPTNO
---------- ---------- ----------
SMITH
800 20
JONES 2975 20
SCOTT
3000 20
ADAMS 1100 20
FORD 3000
20
Elapsed: 00:00:00.02
13:09:53 SCOTT@ test1>alter session set sql_trace
=false;
-----查看用户跟踪生成的trace
13:10:55 SYS@ test1>show parameter dump
NAME TYPE
VALUE
------------------------------------ -----------
------------------------------
user_dump_dest string
/u01/app/oracle/admin/test1/ud
ump
[oracle@rh55 ~]$ ls -lt
/u01/app/oracle/admin/test1/udump/|more
total 2856
-rw-r----- 1 oracle
oinstall 224513 Nov 5 13:10 test1_ora_4879.trc
-rw-r----- 1 oracle oinstall
3023 Nov 5 13:07 test1_ora_4811.trc
---通过tkprof 工具格式化trace 文件
[oracle@rh55 ~]$ tkprof /u01/app/oracle/admin/test1/udump/test1_ora_4879.trc /home/oracle/scott.txt sys=no sort=fchela
TKPROF: Release 10.2.0.1.0 - Production on Mon Nov 5 13:18:00 2012
Copyright (c) 1982, 2005, Oracle. All rights reserved.
[oracle@rh55 ~]$
[oracle@rh55 ~]$ vi scott.txt
TKPROF: Release 10.2.0.1.0 - Production on Mon Nov 5 13:18:00 2012
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Trace file: /u01/app/oracle/admin/test1/udump/test1_ora_4879.trc
Sort
options:
fchela
********************************************************************************
count
= number of times OCI procedure was executed
cpu = cpu time in
seconds executing
elapsed = elapsed time in seconds executing
disk =
number of physical reads of buffers from disk
query = number of buffers
gotten for consistent read
current = number of buffers gotten in current
mode (usually for update)
rows = number of rows processed by the fetch or
execute
call
********************************************************************************
select ename,sal,deptno
from
emp where deptno=10
call count cpu elapsed disk query current
rows
------- ------ -------- ---------- ---------- ---------- ----------
----------
Parse 1 0.01 0.01 0 0
0 0
Execute 1 0.00 0.00 0 0
0 0
Fetch 2 0.00 0.00 0 8
0 3
------- ------ -------- ---------- ---------- ----------
---------- ----------
total 4 0.01 0.01 0
8 0 3
Misses in library cache during parse: 1 ；这条语句第一执行，产生了硬解析
Optimizer mode:
CHOOSE
Parsing user id: 26
Rows Row Source Operation
-------
---------------------------------------------------
3 TABLE ACCESS FULL EMP
(cr=8 pr=0 pw=0 time=603 us)
********************************************************************************
select ename,sal,deptno
from
emp where deptno=20
call count cpu elapsed disk query current
rows
------- ------ -------- ---------- ---------- ---------- ----------
----------
Parse 1 0.01 0.00 0 0
0 0
Execute 1 0.00 0.00 0 0
0 0
Fetch 2 0.00 0.00 0 8
0 5
------- ------ -------- ---------- ---------- ----------
---------- ----------
total 4 0.01 0.00 0
8 0 5
Misses in library cache during parse: 1 ；由于未使用绑定变量，还是硬解析
Optimizer mode:
CHOOSE
Parsing user id: 26
Rows Row Source Operation
-------
---------------------------------------------------
5 TABLE ACCESS FULL EMP
(cr=8 pr=0 pw=0 time=458 us)
------通过dbms_system 跟踪其他用户的sql
1）查看用户的sid
和 serial#
13:42:16 SYS@ test1>select username,sid,serial# from v$session where username is not null;
USERNAME SID
SERIAL#
------------------------------ ---------- ----------
SYS
39 27
SCOTT
38 68
2）对scott 用户的会话进行跟踪
13:42:47 SYS@ test1>exec dbms_system.set_sql_trace_in_session(38,68,sql_trace=>true);
PL/SQL procedure successfully completed.
Elapsed: 00:00:00.10
13:45:14 SYS@ test1>
13:43:13 SCOTT@ test1>var nn number;
13:46:35 SCOTT@ test1>exec :nn:=10;
PL/SQL procedure successfully completed.
Elapsed: 00:00:00.04
13:46:44 SCOTT@ test1>select
empno,ename,sal,deptno from emp where deptno=:nn;
EMPNO ENAME SAL DEPTNO
---------- ----------
---------- ----------
7782 CLARK 2450 10
7839
KING 5000 10
7934 MILLER 1300
10
Elapsed: 00:00:00.04
13:47:04 SCOTT@ test1>exec :nn:=30;
PL/SQL procedure successfully completed.
Elapsed: 00:00:00.02
13:47:12 SCOTT@ test1>select
empno,ename,sal,deptno from emp where deptno=:nn;
EMPNO ENAME SAL DEPTNO
---------- ----------
---------- ----------
7499 ALLEN 1600 30
7521
WARD 1250 30
7654 MARTIN 1250
30
7698 BLAKE 2850 30
7844 TURNER
1500 30
7900 JAMES 950 30
6 rows selected.
Elapsed: 00:00:00.02
13:45:14 SYS@ test1>exec dbms_system.set_sql_trace_in_session(38,68,sql_trace=>false);
PL/SQL procedure successfully completed.
3）查看分析sql
select empno,ename,sal,deptno
from
emp where deptno=:nn
call count cpu elapsed disk query current
rows
------- ------ -------- ---------- ---------- ---------- ----------
----------
Parse 2 0.00 0.00 0 0
0 0
Execute 2 0.00 0.01 0 0
0 0
Fetch 4 0.00 0.00 0 16
0 9
------- ------ -------- ---------- ---------- ----------
---------- ----------
total 8 0.01 0.02 0
16 0 9
Misses in library cache during parse: 1 ；执行一次硬解析，但解析次数为2 次，一次为软解析
Misses
in library cache during execute: 1
Optimizer mode: CHOOSE
Parsing user id:
26
Rows Row Source Operation
-------
---------------------------------------------------
3 TABLE ACCESS FULL EMP
(cr=8 pr=0 pw=0 time=1627 us)
4、调优工具
1）动态性能视图v$xx，动态性能视图是从内存和控制文件读取信息，实时反映了数据库当前的状态，一般用于性能监控和调优
2）数据字典视图：dba_XX，比如表和索引的统计信息
3）statspack
数据库性能统计报告
4）等待事件
5）oracle 提供诊断和调优的包
6）通过对表和索引用analyze 和dbms_stats 工具进行分析，分析后的数据会写入数据字典表里，作为建立执行计划的依据
----统计emp 连同索引
14:07:10 SCOTT@ test1>exec dbms_stats.gather_table_stats(‘SCOTT‘,‘EMP‘,cascade=>true);
PL/SQL procedure successfully completed.
Elapsed: 00:00:01.36
---统计pk_emp 索引，采样20%
14:07:29 SCOTT@ test1>exec
dbms_stats.gather_index_stats(user,‘PK_EMP‘,estimate_percent=>20);
PL/SQL procedure successfully completed.
Elapsed: 00:00:00.09
----统计emp 表所有的数据
14:09:51 SCOTT@ test1>analyze table emp compute
statistics;
Table analyzed.
Elapsed: 00:00:00.10
-----采样20% 统计emp表
14:11:17 SCOTT@ test1>analyze table emp estimate
statistics sample 20 percent;
-----统计index 索引结构
14:13:08 SCOTT@ test1>analyze index pk_emp validate
structure;
Index analyzed.
Elapsed: 00:00:00.12
-----对表中的单个字段进行分析，用于数据在字段上分布倾斜比较严重的情况
案例：
13:33:29 SCOTT@ test1>create table t1 (id int ,name varchar2(20))
;
Table created.
Elapsed: 00:00:01.21
13:35:27 SCOTT@ test1>begin
13:35:35 2
for i in 1..100000 loop
13:35:49 3 insert into t1 values
(i,‘usr‘||to_char(i));
13:36:21 4 end loop;
13:36:33 5
end;
13:36:34 6 /
PL/SQL procedure successfully completed.
Elapsed: 00:00:10.62
13:36:47 SCOTT@ test1>commit;
Commit complete.
Elapsed: 00:00:00.06
13:36:51 SCOTT@ test1>select * from t1 where
rownum <10;
ID NAME
---------- --------------------
1354 usr1354
1355 usr1355
1356 usr1356
1357 usr1357
1358
usr1358
1359 usr1359
1360 usr1360
1361 usr1361
1362 usr1362
9 rows selected.
Elapsed: 00:00:00.15
------更新表，造成数据在name字段上分布严重倾斜
13:37:04 SCOTT@ test1>update t1 set
name=‘tom‘ where id between 100 and 99990;
99891 rows updated.
Elapsed: 00:00:08.19
13:38:45 SCOTT@ test1>COMMIT;
Commit complete.
Elapsed: 00:00:00.01
13:38:58 SCOTT@ test1>select count(*) from t1
where name=‘tom‘;
COUNT(*)
----------
99891
Elapsed: 00:00:00.34
13:39:17 SCOTT@ test1>
13:39:31 SCOTT@
test1>
13:39:31 SCOTT@ test1>analyze table t1 compute statistics;
Table analyzed.
Elapsed: 00:00:01.12
13:39:45 SCOTT@ test1>set autotrace
traceonly;
13:40:02 SCOTT@ test1>select * from t1 where name=‘usr10‘;
Elapsed: 00:00:00.15
Execution
Plan
----------------------------------------------------------
Plan hash
value: 3617692013
--------------------------------------------------------------------------
|
Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
|
--------------------------------------------------------------------------
|
0 | SELECT STATEMENT | | 909 | 7272 | 70 (2)| 00:00:01 |
|*
1 | TABLE ACCESS FULL| T1 | 909 | 7272 | 70 (2)| 00:00:01
|
--------------------------------------------------------------------------
Predicate Information (identified by operation
id):
---------------------------------------------------
1 - filter("NAME"=‘usr10‘)
Statistics
----------------------------------------------------------
1
recursive calls
0 db block gets
311 consistent
gets
0 physical reads
0 redo size
465
bytes sent via SQL*Net to client
384 bytes received via SQL*Net from
client
2 SQL*Net roundtrips to/from client
0 sorts
(memory)
0 sorts (disk)
1 rows processed
13:40:33 SCOTT@ test1>select * from t1 where name=‘tom‘;
99891 rows selected.
Elapsed: 00:00:01.08
Execution
Plan
----------------------------------------------------------
Plan hash
value: 3617692013
--------------------------------------------------------------------------
|
Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
|
--------------------------------------------------------------------------
|
0 | SELECT STATEMENT | | 909 | 7272 | 70 (2)| 00:00:01 |
|*
1 | TABLE ACCESS FULL| T1 | 909 | 7272 | 70 (2)| 00:00:01
|
--------------------------------------------------------------------------
Predicate Information (identified by operation
id):
---------------------------------------------------
1 - filter("NAME"=‘tom‘)
Statistics
----------------------------------------------------------
1
recursive calls
0 db block gets
6954 consistent
gets
0 physical reads
0 redo size
1834181
bytes sent via SQL*Net to client
73633 bytes received via SQL*Net from
client
6661 SQL*Net roundtrips to/from client
0 sorts
(memory)
0 sorts (disk)
99891 rows processed
------在name上建立索引
13:40:55 SCOTT@ test1>create index t1_name_ind on
t1(name) tablespace indx;
Index created.
Elapsed: 00:00:01.52
13:41:39 SCOTT@ test1>select * from t1 where
name=‘usr10‘;
Elapsed: 00:00:00.04
Execution
Plan
----------------------------------------------------------
Plan hash
value: 2446600014
-------------------------------------------------------------------------------------------
|
Id | Operation | Name | Rows | Bytes | Cost (%CPU)|
Time
|
-------------------------------------------------------------------------------------------
|
0 | SELECT STATEMENT | | 909 | 7272 | 5 (0)|
00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| T1 | 909 | 7272
| 5 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN | T1_NAME_IND |
909 | | 2 (0)| 00:00:01
|
-------------------------------------------------------------------------------------------
Predicate Information (identified by operation
id):
---------------------------------------------------
2 - access("NAME"=‘usr10‘)
Statistics
----------------------------------------------------------
1
recursive calls
0 db block gets
4 consistent
gets
1 physical reads
0 redo size
469
bytes sent via SQL*Net to client
384 bytes received via SQL*Net from
client
2 SQL*Net roundtrips to/from client
0 sorts
(memory)
0 sorts (disk)
1 rows processed
------对于tom用户重复值在90000行以上，如果采用索引将不会有好的效率，应该采用全表扫描更合适
13:41:52 SCOTT@
test1>select * from t1 where name=‘tom‘;
99891 rows selected.
Elapsed: 00:00:01.42
Execution
Plan
----------------------------------------------------------
Plan hash
value: 2446600014
-------------------------------------------------------------------------------------------
|
Id | Operation | Name | Rows | Bytes | Cost (%CPU)|
Time
|
-------------------------------------------------------------------------------------------
|
0 | SELECT STATEMENT | | 909 | 7272 | 5 (0)|
00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| T1 | 909 | 7272
| 5 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN | T1_NAME_IND |
909 | | 2 (0)| 00:00:01
|
-------------------------------------------------------------------------------------------
Predicate Information (identified by operation
id):
---------------------------------------------------
2 - access("NAME"=‘tom‘)
Statistics
----------------------------------------------------------
1
recursive calls
0 db block gets
13759 consistent
gets
208 physical reads
0 redo size
2253725
bytes sent via SQL*Net to client
73633 bytes received via SQL*Net from
client
6661 SQL*Net roundtrips to/from client
0 sorts
(memory)
0 sorts (disk)
99891 rows processed
------对name 字段单独做分析（oracle会在name字段上建立直方图或柱状图),oracle
会获得这些字段上数据的分布的具体信息，来制定更好的执行计划
13:42:44 SCOTT@ test1>analyze table t1 compute statistics for columns name;
Table analyzed.
Elapsed: 00:00:01.07
13:45:41 SCOTT@ test1>select * from t1 where
name=‘tom‘;
99891 rows selected.
Elapsed: 00:00:01.05
Execution
Plan
----------------------------------------------------------
Plan hash
value: 3617692013
--------------------------------------------------------------------------
|
Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
|
--------------------------------------------------------------------------
|
0 | SELECT STATEMENT | | 98667 | 770K| 70 (2)| 00:00:01 |
|*
1 | TABLE ACCESS FULL| T1 | 98667 | 770K| 70 (2)| 00:00:01
|
--------------------------------------------------------------------------
Predicate Information (identified by operation
id):
---------------------------------------------------
1 - filter("NAME"=‘tom‘)
Statistics
----------------------------------------------------------
1
recursive calls
0 db block gets
6954 consistent
gets
0 physical reads
0 redo size
1834181
bytes sent via SQL*Net to client
73633 bytes received via SQL*Net from
client
6661 SQL*Net roundtrips to/from client
0 sorts
(memory)
0 sorts (disk)
99891 rows processed
；全表扫描是一个比较合理的执行计划
13:45:52 SCOTT@ test1>select * from t1 where name=‘usr99‘;
Elapsed: 00:00:00.04
Execution
Plan
----------------------------------------------------------
Plan hash
value: 2446600014
-------------------------------------------------------------------------------------------
|
Id | Operation | Name | Rows | Bytes | Cost (%CPU)|
Time
|
-------------------------------------------------------------------------------------------
|
0 | SELECT STATEMENT | | 1 | 8 | 2 (0)|
00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| T1 | 1 | 8
| 2 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN | T1_NAME_IND |
1 | | 1 (0)| 00:00:01
|
-------------------------------------------------------------------------------------------
Predicate Information (identified by operation
id):
---------------------------------------------------
2 - access("NAME"=‘usr99‘)
Statistics
----------------------------------------------------------
1
recursive calls
0 db block gets
4 consistent
gets
2 physical reads
0 redo size
469
bytes sent via SQL*Net to client
384 bytes received via SQL*Net from
client
2 SQL*Net roundtrips to/from client
0 sorts
(memory)
0 sorts (disk)
1 rows processed
13:46:14 SCOTT@ test1>
----统计后的数据会放到dba_tables、dba_indexes、indexe_stats、dba_tab_columns、index_histogram、dba_tab_histogram
----通过autotrace 查看语句的执行计划
14:17:50 SYS@ test1>set autotrace on ；打开trace
14:19:45 SYS@ test1>select ename,sal,deptno from scott.emp where empno=7788;
ENAME SAL DEPTNO
---------- ---------- ----------
SCOTT
3000 20
Elapsed: 00:00:00.02
Execution
Plan
----------------------------------------------------------
Plan hash
value: 2949544139
--------------------------------------------------------------------------------------
|
Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
|
--------------------------------------------------------------------------------------
|
0 | SELECT STATEMENT | | 1 | 13 | 1 (0)|
00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| EMP | 1 | 13 |
1 (0)| 00:00:01 |
|* 2 | INDEX UNIQUE SCAN | PK_EMP | 1 |
| 0 (0)| 00:00:01
|
--------------------------------------------------------------------------------------
Predicate Information (identified by operation
id):
---------------------------------------------------
2 - access("EMPNO"=7788)
Statistics
----------------------------------------------------------
1
recursive calls ；递归调用，从数据字典查询记录
0 db block gets
；DML操作读取的数据块的个数
2 consistent gets ； select
从内存中读取块的次数（一致性读）
0 physical reads ；物理读，从磁盘读取
0 redo size
； 生成redo 大小
526 bytes sent via SQL*Net to client
384 bytes received via SQL*Net from client
2 SQL*Net
roundtrips to/from client
0 sorts (memory) ；在pga
中排序
0 sorts (disk) ；在磁盘上排序（通过临时表空间）
1 rows
processed
set autotrace traceonly ；不返回记录执行结果，只查看执行计划和统计信息
set auto他race
off
14:20:07 SYS@ test1>set autotrace on stat 只查看统计
14:29:11 SYS@ test1>select ename,sal,deptno from scott.emp where empno=7788;
ENAME SAL DEPTNO
---------- ---------- ----------
SCOTT
3000 20
Elapsed: 00:00:00.01
Statistics
----------------------------------------------------------
0
recursive calls
0 db block gets
2 consistent
gets
0 physical reads
0 redo size
526
bytes sent via SQL*Net to client
384 bytes received via SQL*Net from
client
2 SQL*Net roundtrips to/from client
0 sorts
(memory)
0 sorts (disk)
1 rows processed
14:29:18 SYS@ test1>set autotrace on explain ；只查看执行计划
14:29:29 SYS@
test1>select ename,sal,deptno from scott.emp where empno=7788;
ENAME SAL DEPTNO
---------- ---------- ----------
SCOTT
3000 20
Elapsed: 00:00:00.01
Execution
Plan
----------------------------------------------------------
Plan hash
value: 2949544139
--------------------------------------------------------------------------------------
|
Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
|
--------------------------------------------------------------------------------------
|
0 | SELECT STATEMENT | | 1 | 13 | 1 (0)|
00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| EMP | 1 | 13 |
1 (0)| 00:00:01 |
|* 2 | INDEX UNIQUE SCAN | PK_EMP | 1 |
| 0 (0)| 00:00:01
|
--------------------------------------------------------------------------------------
Predicate Information (identified by operation
id):
---------------------------------------------------
2 - access("EMPNO"=7788)
------通过对表分析建立正确的执行计划
案例：
14:05:27 SCOTT@ test1>l
1 select e.ename,e.sal ,d.dname,d.loc from
emp e,dept d
2* where e.deptno=d.deptno
14:05:29 SCOTT@ test1>/
14 rows selected.
Elapsed: 00:00:00.14
Execution
Plan
----------------------------------------------------------
Plan hash
value: 615168685
---------------------------------------------------------------------------
|
Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
|
---------------------------------------------------------------------------
|
0 | SELECT STATEMENT | | 14 | 560 | 7 (15)| 00:00:01 |
|*
1 | HASH JOIN | | 14 | 560 | 7 (15)| 00:00:01 |
| 2
| TABLE ACCESS FULL| DEPT | 4 | 120 | 3 (0)| 00:00:01 |
| 3 |
TABLE ACCESS FULL| EMP | 14 | 140 | 3 (0)| 00:00:01 |
//在dept表上的deptno字段有索引，而此计划走全表扫描，dept应该是没有做过分析。
---------------------------------------------------------------------------
Predicate Information (identified by operation
id):
---------------------------------------------------
1 - access("E"."DEPTNO"="D"."DEPTNO")
Note
-----
- dynamic sampling used for this statement
Statistics
----------------------------------------------------------
213
recursive calls
0 db block gets
133 consistent
gets
7 physical reads
0 redo size
990
bytes sent via SQL*Net to client
384 bytes received via SQL*Net from
client
2 SQL*Net roundtrips to/from client
5 sorts
(memory)
0 sorts (disk)
14 rows processed
-------对表分析后，再查看执行计划
14:05:31 SCOTT@ test1>exec dbms_stats.gather_table_stats(user,‘dept‘,cascade=>true);
PL/SQL procedure successfully completed.
Elapsed: 00:00:00.38
14:06:36 SCOTT@ test1>select e.ename,e.sal
,d.dname,d.loc from emp e,dept d
14:06:48 2 where e.deptno=d.deptno;
14 rows selected.
Elapsed: 00:00:00.02
Execution
Plan
----------------------------------------------------------
Plan hash
value: 351108634
----------------------------------------------------------------------------------------
|
Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
|
----------------------------------------------------------------------------------------
|
0 | SELECT STATEMENT | | 14 | 420 | 4 (0)|
00:00:01 |
| 1 | NESTED LOOPS | | 14 | 420 |
4 (0)| 00:00:01 |
| 2 | TABLE ACCESS FULL | EMP | 14
| 140 | 3 (0)| 00:00:01 |
| 3 | TABLE ACCESS BY INDEX ROWID| DEPT
| 1 | 20 | 1 (0)| 00:00:01 |
|* 4 | INDEX UNIQUE SCAN
| PK_DEPT | 1 | | 0 (0)| 00:00:01
|
----------------------------------------------------------------------------------------
Predicate Information (identified by operation
id):
---------------------------------------------------
4 - access("E"."DEPTNO"="D"."DEPTNO")
Statistics
----------------------------------------------------------
17
recursive calls
0 db block gets
72 consistent gets
；正确的执行计划减少了一致性读
0 physical reads
0 redo size
990 bytes sent via SQL*Net to client
384 bytes received via SQL*Net
from client
2 SQL*Net roundtrips to/from client
0
sorts (memory)
0 sorts (disk)
14 rows processed
14:06:55 SCOTT@ test1>
-------statspack
利用oracle 生成快照（snap），在两个快照之间通过对比生成性能统计报告
1）创建tablespace 存放统计数据
14:50:24 SYS@ test1>create tablespace
perftbs
14:50:46 2 datafile ‘/u01/app/oracle/oradata/test1/perftbs1.dbf‘
size 100m
14:51:14 3 autoextend on maxsize
500m;
2）安装statspack
14:54:40 SYS@ test1>@?/rdbms/admin/spcreate.sql
删除：
14:54:40 SYS@ test1>@?/rdbms/admin/spdrop.sql
3)查看statspack 统计级别
14:58:05 SYS@ test1> select * from
STATS$level_DESCRIPTION
14:58:09 2 ;
SNAP_LEVEL
----------
DESCRIPTION
------------------------------------------------------------------------------------------------------------------------
0
This
level captures general statistics, including rollback segment, row cache, SGA,
system events, background events, se
ssion events, system statistics, wait
statistics, lock statistics, and Latch information
5
This level includes capturing high resource usage SQL
Statements, along with all data captured by lower levels
6
This level includes capturing SQL plan and SQL plan usage
information for high resource usage SQL Statements, along with
all data
captured by lower levels
7
This level captures segment level statistics, including logical
and physical reads, row lock, itl and buffer busy waits,
along with all data
captured by lower levels
SNAP_LEVEL
----------
DESCRIPTION
------------------------------------------------------------------------------------------------------------------------
10
This
level includes capturing Child Latch statistics, along with all data captured by
lower levels
5 rows selected.
-----默认的是level 5
4）修改统计级别
14:43:25 PERFSTAT@ test1 >exec statspack.MODIFY_STATSPACK_PARAMETER(I_SNAP_LEVEL=>7);
PL/SQL procedure successfully completed.
14:58:12 SYS@ test1> execute statspack.snap(i_snap_level=>7);
PL/SQL procedure successfully completed.
Elapsed: 00:00:03.31
15:00:09 SYS@ test1> select SNAP_LEVEL from
stats$snapshot;
SNAP_LEVEL
----------
7
1 row selected.
-----修改statspack snap 级别（修改默认级别）
09:43:48 SYS@ test1>
PL/SQL procedure successfully completed.
Elapsed: 00:00:00.58
09:46:02 SYS@ test1>exec statspack.snap;
PL/SQL procedure successfully completed.
Elapsed: 00:00:06.24
09:46:31 SYS@ test1>exec statspack.snap;
PL/SQL procedure successfully completed.
Elapsed: 00:00:00.97
09:46:40 SYS@ test1>desc
statspack$snapshot
ERROR:
ORA-04043: object statspack$snapshot does not
exist
09:46:54 SYS@ test1>desc stats$snapshot
Name
Null? Type
----------------------------------------------------------------- --------
--------------------------------------------
SNAP_ID
NOT NULL NUMBER
DBID
NOT NULL NUMBER
INSTANCE_NUMBER
NOT NULL NUMBER
SNAP_TIME
NOT NULL DATE
STARTUP_TIME
NOT NULL DATE
SESSION_ID
NOT NULL NUMBER
SERIAL#
NUMBER
SNAP_LEVEL
NUMBER
UCOMMENT
VARCHAR2(160)
EXECUTIONS_TH
NUMBER
PARSE_CALLS_TH
NUMBER
DISK_READS_TH
NUMBER
BUFFER_GETS_TH
NUMBER
SHARABLE_MEM_TH
NUMBER
VERSION_COUNT_TH
NUMBER
SEG_PHY_READS_TH
NOT NULL NUMBER
SEG_LOG_READS_TH
NOT NULL NUMBER
SEG_BUFF_BUSY_TH NOT NULL
NUMBER
SEG_ROWLOCK_W_TH NOT
NULL NUMBER
SEG_ITL_WAITS_TH
NOT NULL NUMBER
SEG_CR_BKS_RC_TH
NUMBER
SEG_CU_BKS_RC_TH
NUMBER
SEG_CR_BKS_SD_TH
NUMBER
SEG_CU_BKS_SD_TH
NUMBER
SNAPSHOT_EXEC_TIME_S
NUMBER
ALL_INIT
VARCHAR2(5)
BASELINE
VARCHAR2(1)
09:47:05 SYS@ test1>select SNAP_ID,SNAP_LEVEL from stats$snapshot;
SNAP_ID SNAP_LEVEL
---------- ----------
21 5
1
7
11 5
12 5
51
7
52 7
31 5
32
5
41 5
9 rows selected.
Elapsed: 00:00:00.02
09:47:33 SYS@ test1>
-------生成statspack报告
14:58:12 SYS@ test1> exec statspack.snap ;
生成快照（在数据稳定期间生成两个快照，建立报告；在性能出现问题时，再生成快照，建立report）
14:58:12 SYS@ test1>@?/rdbms/admin/spreport.sql
------通过两个时间段之间的报告对比来查看数据库性能的变化，再找出原因
AWR 报告使用：
Oracle AWR 介绍
Oracle Database 10g 提供了一个显著改进的工具：自动工作负载信息库
(AWR:Automatic Workload Repository)。Oracle 建议用户用这个取代 Statspack。
AWR 实质上是一个
Oracle 的内置工具，它采集与性能相关的统计数据，并从那些统计数据中导出性能量度，以跟踪潜在的问题。
与 Statspack 不同，快照由一个称为
MMON 的新的后台进程及其从进程自动地每小时采集一次。为了节省空间，采集的数据在 7
天后自动清除。
快照频率和保留时间都可以由用户修改。
它产生两种类型的输出：文本格式（类似于 Statspack 报表的文本格式但来自于 AWR
信息库）和默认的 HTML 格式（拥有到部分和子部分的所有超链接），从而提供了非常用户友好的报表。
AWR
使用几个表来存储采集的统计数据，所有的表都存储在新的名称为 SYSAUX 的特定表空间中的 SYS 模式下，并且以 WRM$_* 和 WRH$_*
的格式命名。前一种类型存储元数据信息（如检查的数据库和采集的快照），后一种类型保存实际采集的统计数据。H 代表“历史数据 (historical)”而 M
代表“元数据 (metadata)”。在这些表上构建了几种带前缀 DBA_HIST_
的视图，这些视图可以用来编写您自己的性能诊断工具。视图的名称直接与表相关；例如，视图 DBA_HIST_SYSMETRIC_SUMMARY
是在WRH$_SYSMETRIC_SUMMARY 表上构建的。
一. AWR使用
SQL>@?/rdbms/admin/awrrpt.sql
Specify the Report Type
~~~~~~~~~~~~~~~~~~~~~~~
Would you like an
HTML report, or a plain text report?
Enter ‘html‘ for an HTML report, or
‘text‘ for plain text
Defaults to ‘html‘
输入 report_type 的值:
Type
Specified: html
Specify the number of days of snapshots to choose from
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Entering the
number of days (n) will result in the most recent
(n) days of snapshots
being listed. Pressing <return> without
specifying a number lists all
completed snapshots.
输入 num_days 的值: 1
Listing the last day‘s Completed
Snapshots
Snap
Instance DB Name Snap Id Snap Started Level
------------ ------------ --------- ------------------ -----
orcl10g
ORCL10G 142 03 7月 2009 08:11 1
143 03 7月 2009 09:00 1
144 03 7月
2009 10:00 1
145 03 7月 2009 11:00 1
146 03 7月 2009 12:01 1
Specify the
Begin and End Snapshot Ids
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
输入
begin_snap 的值: 142
Begin Snapshot Id specified: 142
输入 end_snap 的值:
146
End Snapshot Id specified: 146
Specify the Report Name
~~~~~~~~~~~~~~~~~~~~~~~
The default report file name is
awrrpt_1_142_146.html. To use this name,
press <return> to continue,
otherwise enter an alternative.
输入 report_name 的值: D:\awrrpt_1_142_146.html
Report written to D:\awrrpt_1_142_146.html
二 AWR 操作
1.查看当前的AWR保存策略
SQL> col SNAP_INTERVAL format a20
SQL> col RETENTION format a20
SQL> select * from
dba_hist_wr_control;
DBID SNAP_INTERVAL RETENTION
TOPNSQL
---------- -------------------- -------------------- ----------
262089084 +00000 01:00:00.0 +00007 00:00:00.0 DEFAULT
以上结果表示,每小时产生一个SNAPSHOT，保留7天。
2.调整AWR配置
AWR配置都是通过dbms_workload_repository包进行配置。
2.1
调整AWR产生snapshot的频率和保留策略，如将收集间隔时间改为30 分钟一次。并且保留5天时间（单位都是分钟）：
SQL> exec
dbms_workload_repository.modify_snapshot_settings(interval=>30,
retention=>5*24*60);
2.2 关闭AWR，把interval设为0则关闭自动捕捉快照
SQL> exec
dbms_workload_repository.modify_snapshot_settings(interval=>0);
2.3
手工创建一个快照
SQL> exec DBMS_WORKLOAD_REPOSITORY.CREATE_SNAPSHOT();
2.4
查看快照
SQL> select * from sys.wrh$_active_session_history
2.5
手工删除指定范围的快照
SQL> exec
DBMS_WORKLOAD_REPOSITORY.DROP_SNAPSHOT_RANGE(low_snap_id => 973, high_snap_id
=> 999, dbid => 262089084);
2.6 创建baseline，保存这些数据用于将来分析和比较
SQL>
exec dbms_workload_repository.create_baseline(start_snap_id => 1003,
end_snap_id => 1013, ‘apply_interest_1‘);
2.7 删除baseline
SQL> exec
DBMS_WORKLOAD_REPOSITORY.DROP_BASELINE(baseline_name => ‘apply_interest_1‘,
cascade => FALSE);
2.8 将AWR数据导出并迁移到其它数据库以便于以后分析
SQL> exec
DBMS_SWRF_INTERNAL.AWR_EXTRACT(dmpfile => ‘awr_data.dmp‘, mpdir =>
‘DIR_BDUMP‘, bid => 1003, eid => 1013);
2.9 迁移AWR数据文件到其他数据库
SQL> exec DBMS_SWRF_INTERNAL.AWR_LOAD(SCHNAME => ‘AWR_TEST‘, dmpfile
=> ‘awr_data.dmp‘, dmpdir => ‘DIR_BDUMP‘);
把AWR数据转移到SYS模式中：
SQL> exec DBMS_SWRF_INTERNAL.MOVE_TO_AWR (SCHNAME => ‘TEST‘);
三. AWR 报告分析
3.1 SQL ordered by Elapsed Time
记录了执行总和时间的TOP
SQL(请注意是监控范围内该SQL的执行时间总和，而不是单次SQL执行时间 Elapsed Time = CPU Time + Wait Time)。
Elapsed Time(S):
SQL语句执行用总时长，此排序就是按照这个字段进行的。注意该时间不是单个SQL跑的时间，而是监控范围内SQL执行次数的总和时间。单位时间为秒。Elapsed
Time = CPU Time + Wait Time
CPU Time(s): 为SQL语句执行时CPU占用时间总时长，此时间会小于等于Elapsed
Time时间。单位时间为秒。
Executions: SQL语句在监控范围内的执行次数总计。
Elap per Exec(s):
执行一次SQL的平均时间。单位时间为秒。
% Total DB Time: 为SQL的Elapsed Time时间占数据库总时间的百分比。
SQL ID: SQL语句的ID编号，点击之后就能导航到下边的SQL详细列表中，点击IE的返回可以回到当前SQL ID的地方。
SQL
Module:
显示该SQL是用什么方式连接到数据库执行的，如果是用SQL*Plus或者PL/SQL链接上来的那基本上都是有人在调试程序。一般用前台应用链接过来执行的sql该位置为空。
SQL Text: 简单的sql提示，详细的需要点击SQL ID。
3.2 SQL ordered by CPU Time:
记录了执行占CPU时间总和时间最长的TOP SQL(请注意是监控范围内该SQL的执行占CPU时间总和，而不是单次SQL执行时间)。
3.3
SQL ordered by Gets:
记录了执行占总buffer gets(逻辑IO)的TOP
SQL(请注意是监控范围内该SQL的执行占Gets总和，而不是单次SQL执行所占的Gets)。
3.4 SQL ordered by Reads:
记录了执行占总磁盘物理读(物理IO)的TOP SQL(请注意是监控范围内该SQL的执行占磁盘物理读总和，而不是单次SQL执行所占的磁盘物理读)。
3.5 SQL ordered by Executions:
记录了按照SQL的执行次数排序的TOP
SQL。该排序可以看出监控范围内的SQL执行次数。
3.6 SQL ordered by Parse Calls:
记录了SQL的软解析次数的TOP SQL。说到软解析(soft prase)和硬解析(hard
prase)，就不能不说一下Oracle对sql的处理过程。
3.7 SQL ordered by Sharable Memory:
记录了SQL占用library cache的大小的TOP SQL。Sharable Mem (b)：占用library
cache的大小，单位是byte。
3.8 SQL ordered by Version Count:
记录了SQL的打开子游标的TOP
SQL。
3.9 SQL ordered by Cluster Wait Time:
记录了集群的等待时间的TOP SQL
--------oracle 等待事件
等待事件的源起
等待事件的概念大概是从ORACLE 7.0.12中引入的，大致有100个等待事件。在ORACLE
8.0中这个数目增大到了大约150个，在ORACLE 8I中大约有220个事件，在ORACLE 9IR2中大约有400个等待事件，而在最近ORACLE
10GR2中，大约有874个等待事件。
虽然不同版本和组件安装可能会有不同数目的等待事件，但是这些等待事件都可以通过查询V$EVENT_NAME视图获得
1). 空闲等待事件指ORACLE正等待某种工作，在诊断和优化数据库的时候，不用过多注意这部分事件。
2).
非空闲等待事件专门针对ORACLE的活动，指数据库任务或应用运行过程中发生的等待，这些等待事件是在调整数据库的时候需要关注与研究的
常见的空闲事件有:
* dispatcher timer
* lock element cleanup
* Null event
*
parallel query dequeue wait
* parallel query idle wait - Slaves
* pipe
get
* PL/SQL lock timer
* pmon timer- pmon
* rdbms ipc
message
* slave wait
* smon timer
* SQL*Net break/reset to
client
* SQL*Net message from client
* SQL*Net message to client
*
SQL*Net more data to client
* virtual circuit status
* client
message
一些常见的非空闲等待事件有:
* db file scattered read
* db file sequential read
* buffer busy
waits
* free buffer waits
* enqueue
* latch free
* log file
parallel write
* log file sync
-----等待事件的查看
案例：
Elapsed: 00:00:00.01
13:33:28 SCOTT@ test1>begin
13:54:46 2 for
i in 1..100000 loop
13:54:46 3 execute immediate ‘insert into t1 values
(‘||i||‘) ‘;
13:54:46 4 end loop;
13:54:46 5 end;
13:54:46
6 /
PL/SQL procedure successfully completed.
Elapsed: 00:01:46.54
13:56:34 SCOTT@ test1>
-----对某一会话事件监控
13:56:00 SYS@ test1>select username,sid,serial# from v$session where username is not null;
USERNAME SID
SERIAL#
------------------------------ ---------- ----------
SCOTT
34 52
SYS
23 35
SYS 39 27
SYS
24 785
Elapsed: 00:00:00.17
13:56:16 SYS@ test1>clear scr
13:56:31 SYS@ test1>select sid,event,total_waits,average_wait from v$session_event where sid=34;
SID EVENT
TOTAL_WAITS AVERAGE_WAIT
----------
---------------------------------------------------------------- -----------
------------
34 latch: cache buffers chains
1 1.03
34 enq: RO - fast object reuse
1 .72
34 log file switch
completion 6 8.52
34 log file sync
3 .14
34 db file sequential read
12 2.32
34 latch: library cache
2 22.59
34
SQL*Net message to client 33
0
34 SQL*Net message from client
32 7703.96
34 events in waitclass Other
4 10.87
9 rows selected.
Elapsed: 00:00:00.03
13:57:03 SYS@ test1>
----对整个实例事件监控
13:53:14 SYS@ test1>col event for a50
----insert事务发生前
13:53:32 SYS@ test1>r
1 select
event,total_waits,total_timeouts,time_waited,average_wait
2 from
v$system_event
3* where event like ‘%buffer%‘
EVENT TOTAL_WAITS TOTAL_TIMEOUTS
TIME_WAITED AVERAGE_WAIT
--------------------------------------------------
----------- -------------- ----------- ------------
latch: cache buffers
chains 1 0 1
1.02
buffer busy waits 1
0 0 .01
log buffer space
2 1 182 90.75
latch: cache buffers
lru chain 5 0 1
.2
Elapsed: 00:00:00.01
13:53:32 SYS@ test1>/
------insert事务发生后
EVENT
TOTAL_WAITS TOTAL_TIMEOUTS TIME_WAITED
AVERAGE_WAIT
-------------------------------------------------- -----------
-------------- ----------- ------------
latch: cache buffers chains
2 0 2 1.03
buffer busy
waits 2 0 0
.07
log buffer space 2
1 182 90.75
latch: cache buffers lru chain
5 0 1 .2
Elapsed: 00:00:00.01
13:57:28 SYS@ test1>
原文地址：http://www.cnblogs.com/gispf/p/3725446.html
