Oracle 10053 事件

一. 10053事件

当一个SQL出现性能问题的时候,可以使用SQL_TRACE 或者 10046事件来跟踪SQL. 通过生成的trace来了解SQL的执行过程。

 

Oracle SQL Trace 10046事件

http://blog.csdn.net/tianlesoftware/archive/2010/09/02/5857023.aspx

 

Event 10053 执行计划绑定变量 Bind peeking

http://blog.csdn.net/tianlesoftware/archive/2010/04/30/5544307.aspx

 

Oracle 跟踪事件 set event

http://blog.csdn.net/tianlesoftware/archive/2009/12/13/4977827.aspx

 

 

现在来看一下10053事件。10053事件也是非公开的,在官网上也找不到相关信息。  我们在查看一条SQL的执行计划的时候,只能看到CBO 最终告诉我们的执行计划结果,但是不知道CBO 是根据什么来做的。 如果遇到了执行计划失真,如:一个SQL语句,很明显oracle应该使用索引,但是执行计划却没有使用索引。无法进行分析判断。

而10053事件就提供了这样的功能。它产生的trace文件提供了Oracle如何选择执行计划,为什么会得到这样的执行计划信息。

 

10053事件生成trace文件目录和SQL_TRACE一样。

在Oracle 10g中,SQL_TRACE生成的trace文件默认路劲是$ORACLE_BASE/admin/SID/udump.       

在Oracle 11g,trace 默认路径在:$ORACLE_BASE/diag/rdbms/orcl/orcl/trace目录下

 

对于10053事件的trace文件,我们只能直接阅读原始的trace文件,不能使用tkprof工具来处理,tkprof工具只能用来处理sql_trace 和 10046事件产生的trace文件。

 

10053事件有两个级别:

         Level 22级是1级的一个子集,它包含以下内容:

                            Column statistics

Single Access Paths

Join Costs

Table Joins Considered

Join Methods Considered (NL/MS/HA)

         Level 11级比2级更详细,它包含2级的所有内容,在加如下内容:

                            Parameters used by the optimizer

Index statistics

 

启用10053事件:

         ALTER SESSION SET EVENTS='10053 trace name context forever, level 1';

ALTER SESSION SET EVENTS='10053 trace name context forever, level 2';

 

关闭10053事件:

ALTER SESSION SET EVENTS '10053 trace name context off';

 

 

说明:

1sqlplus中打开autotrace看到的执行计划实际上是用explain plan 命令得到的,explain plan 命令不会进行bind peeking。应该通过v$sql_plan查看SQL的真实的执行计划。

210053只对CBO有效,而且如果一个sql语句已经解析过,就不会产生新的trace信息。

 

 

二.示例:

1.       确定当前的trace文件

 

1.1 设定trace文件标识

SQL> alter session set tracefile_identifier='怀宁';

会话已更改。

 

设置标识的目的就是方便我们查找生成的trace文件。我们只需要在trace目录查找文件名里带有标识的文件即可。

 

1.2直接用如下SQL直接查出,当前的trace文件名。

 

/* Formatted on 2010/9/1 23:56:24 (QP5 v5.115.810.9015) */

SELECT      d.VALUE

         || '/'

         || LOWER (RTRIM (i.INSTANCE, CHR (0)))

         || '_ora_'

         || p.spid

         || '.trc'

            AS "trace_file_name"

  FROM   (SELECT   p.spid

            FROM   v$mystat m, v$session s, v$process p

           WHERE   m.statistic# = 1 AND s.SID = m.SID AND p.addr = s.paddr) p,

         (SELECT   t.INSTANCE

            FROM   v$thread t, v$parameter v

           WHERE   v.NAME = 'thread'

                   AND (v.VALUE = 0 OR t.thread# = TO_NUMBER (v.VALUE))) i,

         (SELECT   VALUE

            FROM   v$parameter

           WHERE   NAME = 'user_dump_dest') d;

 

2.       启动10053事件

SQL> ALTER SESSION SET EVENTS='10053 trace name context forever, level 1';

 

3.       执行事务

SQL> select * from all_tables where table_name='T';

 

4.       关闭10053事件

SQL> ALTER SESSION SET EVENTS '10053 trace name context off';

 

 

三.查看生成的trace文件

         因为我们在做之前设置了标识,所以直接进入trace目录,找到含有 ‘怀宁’标识的trace 文件。

 

Trace file d:/app/administrator/diag/rdbms/orcl/orcl/trace/orcl_ora_3756_怀宁.trc

Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production

With the Partitioning, OLAP, Data Mining and Real Application Testing options

Windows NT Version V6.1 

CPU                 : 2 - type 586, 2 Physical Cores

Process Affinity    : 0x0x00000000

Memory (Avail/Total): Ph:1570M/4095M, Ph+PgF:4126M/8188M, VA:2874M/4095M

Instance name: orcl

Redo thread mounted by this instance: 1

Oracle process number: 32

Windows thread id: 3756, image: ORACLE.EXE (SHAD)

 

 

*** 2010-09-02 15:09:16.677

*** SESSION ID:(23.3388) 2010-09-02 15:09:16.677

*** CLIENT ID:() 2010-09-02 15:09:16.677

*** SERVICE NAME:(SYS$USERS) 2010-09-02 15:09:16.677

*** MODULE NAME:(sqlplus.exe) 2010-09-02 15:09:16.677

*** ACTION NAME:() 2010-09-02 15:09:16.677

 

 

*** TRACE CONTINUED FROM FILE d:/app/administrator/diag/rdbms/orcl/orcl/trace/orcl_ora_3756.trc ***

 

Registered qb: SEL$1 0xdab3a30 (PARSER)

---------------------

QUERY BLOCK SIGNATURE

---------------------

  signature (): qb_name=SEL$1 nbfros=1 flg=0

    fro(0): flg=5 objn=3232 hint_alias="ALL_TABLES"@"SEL$1"

 

Registered qb: SEL$2 0xdab1a9c (PARSER)

---------------------

QUERY BLOCK SIGNATURE

---------------------

  signature (): qb_name=SEL$2 nbfros=11 flg=0

    fro(0): flg=4 objn=18 hint_alias="CO"@"SEL$2"

    fro(1): flg=4 objn=22 hint_alias="CU"@"SEL$2"

    fro(2): flg=4 objn=18 hint_alias="CX"@"SEL$2"

    fro(3): flg=4 objn=132 hint_alias="DS"@"SEL$2"

    fro(4): flg=4 objn=4294951198 hint_alias="KSPPCV"@"SEL$2"

    fro(5): flg=4 objn=4294950998 hint_alias="KSPPI"@"SEL$2"

    fro(6): flg=4 objn=18 hint_alias="O"@"SEL$2"

    fro(7): flg=4 objn=14 hint_alias="S"@"SEL$2"

    fro(8): flg=4 objn=4 hint_alias="T"@"SEL$2"

    fro(9): flg=4 objn=16 hint_alias="TS"@"SEL$2"

    fro(10): flg=4 objn=22 hint_alias="U"@"SEL$2"

 

Registered qb: SEL$3 0xf8a701c (PARSER)

---------------------

QUERY BLOCK SIGNATURE

---------------------

  signature (): qb_name=SEL$3 nbfros=1 flg=0

    fro(0): flg=4 objn=61 hint_alias="OA"@"SEL$3"

 

Registered qb: SEL$4 0xf8a6acc (PARSER)

---------------------

QUERY BLOCK SIGNATURE

---------------------

  signature (): qb_name=SEL$4 nbfros=1 flg=0

    fro(0): flg=4 objn=4294951024 hint_alias="X$KZSRO"@"SEL$4"

 

Registered qb: SEL$5 0xf8a6384 (PARSER)

---------------------

QUERY BLOCK SIGNATURE

---------------------

  signature (): qb_name=SEL$5 nbfros=1 flg=0

    fro(0): flg=5 objn=4294950942 hint_alias="V$ENABLEDPRIVS"@"SEL$5"

 

Registered qb: SEL$6 0xf8ba570 (PARSER)

---------------------

QUERY BLOCK SIGNATURE

---------------------

  signature (): qb_name=SEL$6 nbfros=1 flg=0

    fro(0): flg=5 objn=4294951295 hint_alias="GV$ENABLEDPRIVS"@"SEL$6"

 

Registered qb: SEL$7 0xf8b9c50 (PARSER)

---------------------

QUERY BLOCK SIGNATURE

---------------------

  signature (): qb_name=SEL$7 nbfros=1 flg=0

    fro(0): flg=4 objn=4294951025 hint_alias="X$KZSPR"@"SEL$7"

 

SPM: statement not found in SMB

 

**************************

Automatic degree of parallelism (ADOP)

**************************

Automatic degree of parallelism is disabled: Parameter.

 

PM: Considering predicate move-around in query block SEL$1 (#0)

**************************

Predicate Move-Around (PM)

**************************

OPTIMIZER INFORMATION

 

******************************************

----- Current SQL Statement for this session (sql_id=57m60mu8c3w33) -----

select * from all_tables where table_name='T'

*******************************************

Legend

The following abbreviations are used by optimizer trace.

CBQT - cost-based query transformation

JPPD - join predicate push-down

OJPPD - old-style (non-cost-based) JPPD

FPD - filter push-down

PM - predicate move-around

CVM - complex view merging

SPJ - select-project-join

SJC - set join conversion

SU - subquery unnesting

OBYE - order by elimination

OST - old style star transformation

ST - new (cbqt) star transformation

CNT - count(col) to count(*) transformation

JE - Join Elimination

JF - join factorization

SLP - select list pruning

DP - distinct placement

qb - query block

LB - leaf blocks

DK - distinct keys

LB/K - average number of leaf blocks per key

DB/K - average number of data blocks per key

CLUF - clustering factor

NDV - number of distinct values

Resp - response cost

Card - cardinality

Resc - resource cost

NL - nested loops (join)

SM - sort merge (join)

HA - hash (join)

CPUSPEED - CPU Speed

IOTFRSPEED - I/O transfer speed

IOSEEKTIM - I/O seek time

SREADTIM - average single block read time

MREADTIM - average multiblock read time

MBRC - average multiblock read count

MAXTHR - maximum I/O system throughput

SLAVETHR - average slave I/O throughput

dmeth - distribution method

  1: no partitioning required

  2: value partitioned

  4: right is random (round-robin)

  128: left is random (round-robin)

  8: broadcast right and partition left

  16: broadcast left and partition right

  32: partition left using partitioning of right

  64: partition right using partitioning of left

  256: run the join in serial

  0: invalid distribution method

sel - selectivity

ptn - partition

***************************************

PARAMETERS USED BY THE OPTIMIZER

********************************

  *************************************

  PARAMETERS WITH ALTERED VALUES

  ******************************

Compilation Environment Dump

Bug Fix Control Environment

 

….

 

Starting SQL statement dump

 

user_id=0 user_name=SYS module=sqlplus.exe action=

sql_id=57m60mu8c3w33 plan_hash_value=-564731517 problem_type=3

----- Current SQL Statement for this session (sql_id=57m60mu8c3w33) -----

select * from all_tables where table_name='T'

sql_text_length=46

sql=select * from all_tables where table_name='T'

----- Explain Plan Dump -----

----- Plan Table -----

 

============

Plan Table

============

-----------------------------------------------------------------+-----------------------------------+

| Id  | Operation                               | Name           | Rows  | Bytes | Cost  | Time      |

-----------------------------------------------------------------+-----------------------------------+

| 0   | SELECT STATEMENT                        |                |       |       |   124 |           |

| 1   |  FILTER                                 |                |       |       |       |           |

| 2   |   HASH JOIN                             |                |     2 |  4704 |   124 |  00:00:02 |

| 3   |    MERGE JOIN CARTESIAN                 |                |     2 |   674 |   124 |  00:00:02 |

| 4   |     NESTED LOOPS OUTER                  |                |     2 |   564 |   124 |  00:00:02 |

| 5   |      NESTED LOOPS OUTER                 |                |     2 |   530 |   122 |  00:00:02 |

| 6   |       NESTED LOOPS OUTER                |                |     2 |   514 |   120 |  00:00:02 |

| 7   |        NESTED LOOPS OUTER               |                |     2 |   454 |   118 |  00:00:02 |

| 8   |         NESTED LOOPS OUTER              |                |     2 |   364 |   116 |  00:00:02 |

| 9   |          NESTED LOOPS                   |                |     2 |   318 |   114 |  00:00:02 |

| 10  |           NESTED LOOPS                  |                |     2 |   280 |   112 |  00:00:02 |

| 11  |            NESTED LOOPS                 |                |     2 |   106 |   111 |  00:00:02 |

| 12  |             TABLE ACCESS BY INDEX ROWID | OBJ$           |     2 |    72 |   109 |  00:00:02 |

| 13  |              INDEX SKIP SCAN            | I_OBJ2         |     2 |       |   107 |  00:00:02 |

| 14  |             TABLE ACCESS CLUSTER        | USER$          |     1 |    17 |     1 |  00:00:01 |

| 15  |              INDEX UNIQUE SCAN          | I_USER#        |     1 |       |     0 |           |

| 16  |            TABLE ACCESS CLUSTER         | TAB$           |     1 |    87 |     1 |  00:00:01 |

| 17  |             INDEX UNIQUE SCAN           | I_OBJ#         |     1 |       |     0 |           |

| 18  |           TABLE ACCESS CLUSTER          | TS$            |     1 |    19 |     1 |  00:00:01 |

| 19  |            INDEX UNIQUE SCAN            | I_TS#          |     1 |       |     0 |           |

| 20  |          TABLE ACCESS BY INDEX ROWID    | DEFERRED_STG$  |     1 |    23 |     1 |  00:00:01 |

| 21  |           INDEX UNIQUE SCAN             | I_DEFERRED_STG1|     1 |       |     0 |           |

| 22  |         TABLE ACCESS CLUSTER            | SEG$           |     1 |    45 |     1 |  00:00:01 |

| 23  |          INDEX UNIQUE SCAN              | I_FILE#_BLOCK# |     1 |       |     0 |           |

| 24  |        TABLE ACCESS BY INDEX ROWID      | OBJ$           |     1 |    30 |     2 |  00:00:01 |

| 25  |         INDEX RANGE SCAN                | I_OBJ1         |     1 |       |     1 |  00:00:01 |

| 26  |       INDEX RANGE SCAN                  | I_OBJ1         |     1 |     8 |     1 |  00:00:01 |

| 27  |      TABLE ACCESS CLUSTER               | USER$          |     1 |    17 |     1 |  00:00:01 |

| 28  |       INDEX UNIQUE SCAN                 | I_USER#        |     1 |       |     0 |           |

| 29  |     BUFFER SORT                         |                |     1 |    55 |   123 |  00:00:02 |

| 30  |      FIXED TABLE FULL                   | X$KSPPI        |     1 |    55 |     0 |           |

| 31  |    FIXED TABLE FULL                     | X$KSPPCV       |   100 |  197K |     0 |           |

| 32  |   NESTED LOOPS                          |                |     1 |    21 |     2 |  00:00:01 |

| 33  |    INDEX RANGE SCAN                     | I_OBJAUTH1     |     1 |     8 |     2 |  00:00:01 |

| 34  |    FIXED TABLE FULL                     | X$KZSRO        |     1 |    13 |     0 |           |

| 35  |   FIXED TABLE FULL                      | X$KZSPR        |     1 |    26 |     0 |           |

-----------------------------------------------------------------+-----------------------------------+

 

…..

 

 

 

小结:

         CBO 一定是选择代价最低的数据访问路径作为SQL的执行计划。 如果觉得CBO做出的执行计划不是最优的,就应该去分析。 这时就用到了10053事件。 我们需要关注CBO选择的每一个代价最低的数据访问方式,以及提供给CBO的分析信息是否真实。

        

CBO 只是一个数学模型,它只是机械地将收集到的各种信息通过固定的方式进行计算,如果我们提供给CBO的信息是准确的,那么CBO 就能计算出最优的执行计划(排除bug)。

        

         10053事件没有10046事件用的多,比如我们分析SQL,主要还是看SQL的执行计划和SQL_TRACE信息。 但是如果想了解CBO的内部,还得通过10053事件,从10053事件的trace文件中,我们可以深入的了解CBO的内部,了解CBO是如何工作的,根据什么依据得出最终的执行计划。


Forward from David's http://blog.csdn.net/tianlesoftware/article/details/5859027


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