10053 otw

Doug Burns [email protected]://oracledoug.com@orcldoug#OTW#OakTable

Introduction What How Why Structure Example Conclusions and References

01/10/2013

Who am I? Why am I talking? Setting Expectations

01/10/2013

I am Doug Doug I am << Dr Seuss Edition

Actually I am Douglas

… or, if you're Scottish, Dougie or Doogie

I'm not from England You will have probably noticed that already

I don't know many Scottish people who do glowing introductions about their all-round genius!

But, amongst other things, I am …

01/10/2013

01/10/2013

A long time ago in a galaxy far, far away ….

"A look under the hood of CBO: The 10053 Event" Wolfgang Breitling (see References)

Time passes & beers are consumed & conversations follow … You almost never need to use 10053 trace files

They are far too long and complex to understand

… and yet … I find myself using them more often

I think they're becoming easier to understand

01/10/2013

01/10/2013

10053 files, like most Oracle trace files are Useful in specific situations

Very detailed and informative

Relatively easy to generate

They are also Usually unnecessary

Undocumented

Subject to change over time

Complex in places

01/10/2013


01/10/2013

Contains a record of the Cost Based Optimizer decision making process and the various inputs used Hard Parse Time

As we'll see, it contains Server configuration items that influence the CBO

Object and System Statistics used by calculations

Execution Plan Steps that were considered and accepted▪ Resulting in final overall execution plan

Execution Plan Steps that were considered and rejected▪ Including the reasons why

01/10/2013


01/10/2013

By enabling event 10053 using any of the usual methods Run (or Explain) the SQL statement Disable event Find trace file in user_dump_dest

01/10/2013

show parameter user_dump_dest

ALTER SESSION SET tracefile_identifier='EXAMPLE1_10053';

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

SELECT * FROM dual;

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

The statement must be hard-parsed The statement must not have been run before

Plan has been aged out of cursor cache

Shared pool has been flushed

New version of the statement by adding a unique comment

01/10/2013


ALTER SESSION SET tracefile_identifier='EXAMPLE1_10053_1';

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

SELECT /* EXAMPLE1_1 */ * FROM dual;

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

Oracle 11g introduces a new tracing infrastructure

Can be accessed using ALTER SESSION

ORADEBUG

DBMS_SQLDIAG.DUMP_TRACE▪ Does not require Diagnostics Pack license

01/10/2013

Replacement for original method of setting event 10053

Main 10053-related Options SQL_Compiler and SQL_Optimizer

01/10/2013


ALTER SESSION SET tracefile_identifier='EXAMPLE1_2_OPTTRACE';

ALTER SESSION SET events 'trace [SQL_Compiler.*]';


ALTER SESSION SET events 'trace [SQL_Compiler.*] off';

There are also sub-options

01/10/2013

SQL> oradebug doc component SQL_Compiler

SQL_Compiler SQL Compiler

SQL_Parser SQL Parser (qcs)

SQL_Semantic SQL Semantic Analysis (kkm)

SQL_Optimizer SQL Optimizer

SQL_Transform SQL Transformation (kkq, vop, nso)

SQL_MVRW SQL Materialized View Rewrite

SQL_VMerge SQL View Merging (kkqvm)

SQL_Virtual SQL Virtual Column (qksvc, kkfi)

SQL_APA SQL Access Path Analysis (apa)

SQL_Costing SQL Cost-based Analysis (kko, kke)

SQL_Parallel_Optimization SQL Parallel Optimization (kkopq)

SQL_Code_Generator SQL Code Generator (qka, qkn, qke,

kkfd, qkx)

SQL_Parallel_Compilation SQL Parallel Compilation (kkfd)

SQL_Expression_Analysis SQL Expression Analysis (qke)

SQL_Plan_Management SQL Plan Managment (kkopm)

MPGE MPGE (qksctx)

What if you want to trace just one SQL statement that a Session executes?

Perhaps inside a PL/SQL procedure or function Can also specify SQL_ID Still relies on Hard Parse

01/10/2013


ALTER SESSION SET tracefile_identifier='EXAMPLE2_OPTTRACE';

ALTER SESSION SET events 'trace [SQL_Compiler.*][sql:37cv4d33vbu8h]';


ALTER SESSION SET events 'trace [SQL_Compiler.*] off';

What if you want to trace just one SQL statement and you don't know which session will execute it?

Can enable System-wide tracing using ALTER SYSTEM

Still relies on Hard Parse

01/10/2013


ALTER SYSTEM SET events 'trace [SQL_Compiler.*][sql:bhqn6d93r5r03]';

ALTER SYSTEM SET events 'trace [SQL_Compiler.*] off';

Solves several issues Can show optimizer trace file for a statement that has already been

executed and exists in the cursor cache

Can force hard parse of the statement

Can only use Optimizer or Compiler

01/10/2013

BEGIN

dbms_sqldiag.dump_trace(

p_sql_id => '37cv4d33vbu8h',

p_child_number => 0,

p_component => 'Compiler',

p_file_id => 'EXAMPLE1_OPTTRACE');

END;

/

01/10/2013

Enabling tracing for cur#=10 sqlid=8rhfhbwtndmgc recursive

Parsing cur#=10 sqlid=8rhfhbwtndmgc len=61

sql=/* SQL Analyze(216,0) */ SELECT /* EXAMPLE1_2 */ * FROM dual

End parsing of cur#=10 sqlid=8rhfhbwtndmgc

Semantic Analysis cur#=10 sqlid=8rhfhbwtndmgc

OPTIMIZER INFORMATION

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

----- Current SQL Statement for this session (sql_id=8rhfhbwtndmgc) -----

/* SQL Analyze(216,0) */ SELECT /* EXAMPLE1_2 */ * FROM dual

----- PL/SQL Stack -----

----- PL/SQL Call Stack -----

object line object

handle number name

0xee579040 145 package body SYS.DBMS_SQLTUNE_INTERNAL

0xee579040 12085 package body SYS.DBMS_SQLTUNE_INTERNAL

0xee814bc0 1229 package body SYS.DBMS_SQLDIAG

0xe8c34ab0 2 anonymous block

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


01/10/2013

Many ways of viewing the execution plan used for a statement 10046 Trace File

DBMS_XPLAN - combined with /*+ gather_plan_statistics */

Real-Time SQL Monitoring

Modern options allow comparison of Estimated vs. Actual row source cardinalities E-Rows vs. A-Rows

Experience and data knowledge allow educated guesses about what is 'going wrong'

01/10/2013

No real overhead

Only happens at hard parse

Sounds crazy, but even if it doesn't help you, it doesn't hurt to look As long as you don't look for too long!

01/10/2013

You've never wondered why that optimiser won't play?

Sometimes they are the only way of knowing why the CBO made a specific decision

Particularly useful tools here are trace files for 'good' and 'bad' plans and a visual diff tool

They are a great way of learning about the CBO and particularly any new features

Oracle Support/Optimizer Development Group!

01/10/2013


01/10/2013

Standard Trace File Pre-amble Query Block Assignment SQL Plan Management Parallel Query/Auto-DOP Predicate Move-Around Optimizer Information Query Transformations Peeked Binds Statistics Computations – Access Paths and Join Orders SQL Statement and Execution Plan dump

01/10/2013

01/10/2013

Trace file

/app/ora/local/admin/TEST1102/diag/rdbms/TEST1102_doug/TEST1102/trace/TEST1102_ora_1

450_DOUG_TEST2.trc

Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production

With the Partitioning, Automatic Storage Management, OLAP, Data Mining

and Real Application Testing options

ORACLE_HOME = /app/ora/local/product/11.2.0.2/db_4

System name: Linux

Node name: doug

Release: 2.6.18-194.11.4.el5

Version: #1 SMP Fri Sep 17 04:57:05 EDT 2010

Machine: x86_64

Instance name: TEST1102

Redo thread mounted by this instance: 1

Oracle process number: 52

Unix process pid: 1450, image: oracle@doug

*** 2013-03-18 10:59:58.774

*** SESSION ID:(139.79) 2013-03-18 10:59:58.774

*** CLIENT ID:() 2013-03-18 10:59:58.774

*** SERVICE NAME:(SYS$USERS) 2013-03-18 10:59:58.774

*** MODULE NAME:(TOAD 10.6.1.3) 2013-03-18 10:59:58.774

*** ACTION NAME:() 2013-03-18 10:59:58.774

01/10/2013

Registered qb: SEL$1 0xad486a80 (PARSER)

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

QUERY BLOCK SIGNATURE

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

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

fro(0): flg=4 objn=116 hint_alias="DUAL"@"SEL$1"

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)

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

01/10/2013

OPTIMIZER INFORMATION

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

----- Current SQL Statement for this session (sql_id=a5ks9fhw2v9s1) -----

select * from dual

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

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

Oracle 8.1.7 ≈ 50 Oracle 11.2.0.3 > 300

01/10/2013

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

PARAMETERS USED BY THE OPTIMIZER

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

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

PARAMETERS WITH ALTERED VALUES

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

Compilation Environment Dump

_pga_max_size = 2097152 KB

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

PARAMETERS WITH DEFAULT VALUES

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

Compilation Environment Dump

optimizer_mode_hinted = false

optimizer_features_hinted = 0.0.0

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

PARAMETERS IN OPT_PARAM HINT

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

The Optimizer Development group are Busy Bees!

As they introduce fixes, they number them and store information about them in V$SYSTEM_FIX_CONTROL

Can enable/disable … http://tinyurl.com/5r9zrse Coskan Blog Post

01/10/2013

Bug Fix Control Environment

fix 3834770 = 1

fix 3746511 = enabled




fix 2194204 = disabled


http://tinyurl.com/5r9zrse

01/10/2013

Considering Query Transformations on query block SEL$1 (#0)

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

Query transformations (QT)

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

JF: Checking validity of join factorization for query block SEL$1 (#0)

JF: Bypassed: not a UNION or UNION-ALL query block.

ST: not valid since star transformation parameter is FALSE

TE: Checking validity of table expansion for query block SEL$1 (#0)

TE: Bypassed: No partitioned table in query block.

CBQT bypassed for query block SEL$1 (#0): no complex view, sub-queries or UNION

(ALL) queries.

CBQT: Validity checks failed for a5ks9fhw2v9s1.

CSE: Considering common sub-expression elimination in query block SEL$1 (#0)

Exadata/11g Upgrade project optimizer_features_enable – 10.2.0.4 Cost-based query transformation http://tinyurl.com/c6wdhxv - Jonathan Lewis Blog Post

http://tinyurl.com/c6wdhxv

01/10/2013

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

Common Subexpression elimination (CSE)

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

CSE: CSE not performed on query block SEL$1 (#0).

OBYE: Considering Order-by Elimination from view SEL$1 (#0)

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

Order-by elimination (OBYE)

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

OBYE: OBYE bypassed: no order by to eliminate.

CVM: Considering view merge in query block SEL$1 (#0)

query block SEL$1 (#0) unchanged

Considering Query Transformations on query block SEL$1 (#0)

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

Query transformations (QT)

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

JF: Checking validity of join factorization for query block SEL$1 (#0)

JF: Bypassed: not a UNION or UNION-ALL query block.

ST: not valid since star transformation parameter is FALSE

TE: Checking validity of table expansion for query block SEL$1 (#0)

TE: Bypassed: No partitioned table in query block.

CBQT bypassed for query block SEL$1 (#0): no complex view, sub-queries or UNION

(ALL) queries.

CBQT: Validity checks failed for a5ks9fhw2v9s1.

01/10/2013

SYSTEM STATISTICS INFORMATION

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

Using NOWORKLOAD Stats

CPUSPEEDNW: 1416 millions instructions/sec (default is 100)

IOTFRSPEED: 4096 bytes per millisecond (default is 4096)

IOSEEKTIM: 10 milliseconds (default is 10)

MBRC: -1 blocks (default is 32)

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

BASE STATISTICAL INFORMATION

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

Table Stats::

Table: DUAL Alias: DUAL

#Rows: 1 #Blks: 1 AvgRowLen: 2.00 ChainCnt: 0.00

Access path analysis for DUAL

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

SINGLE TABLE ACCESS PATH

Single Table Cardinality Estimation for DUAL[DUAL]

Table: DUAL Alias: DUAL

Card: Original: 1.000000 Rounded: 1 Computed: 1.00 Non Adjusted: 1.00

Access Path: TableScan

Cost: 2.00 Resp: 2.00 Degree: 0

Cost_io: 2.00 Cost_cpu: 9893

Resp_io: 2.00 Resp_cpu: 9893

Best:: AccessPath: TableScan

Cost: 2.00 Degree: 1 Resp: 2.00 Card: 1.00 Bytes: 0

01/10/2013

OPTIMIZER STATISTICS AND COMPUTATIONS

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

GENERAL PLANS

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

Considering cardinality-based initial join order.

Permutations for Starting Table :0

Join order[1]: DUAL[DUAL]#0

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

Best so far: Table#: 0 cost: 2.0005 card: 1.0000 bytes: 2

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

(newjo-stop-1) k:0, spcnt:0, perm:1, maxperm:2000

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

Number of join permutations tried: 1

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

This is the section that gets very complicated very quickly!

01/10/2013

Plan Table

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

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

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

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

| 0 | SELECT STATEMENT | | | | 2 | |

| 1 | TABLE ACCESS FULL | DUAL | 1 | 2 | 2 | 00:00:01 |

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

Content of other_xml column

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

db_version : 11.2.0.2

parse_schema : RRS_CORE_DBO

plan_hash : 272002086

plan_hash_2 : 4017058736

Outline Data:

/*+

BEGIN_OUTLINE_DATA

IGNORE_OPTIM_EMBEDDED_HINTS

OPTIMIZER_FEATURES_ENABLE('11.2.0.2')

DB_VERSION('11.2.0.2')

ALL_ROWS

OUTLINE_LEAF(@"SEL$1")

FULL(@"SEL$1" "DUAL"@"SEL$1")

END_OUTLINE_DATA

*/


01/10/2013

Many ways of viewing the execution plan used for a statement

All show you the numbers that the CBO is using and the resulting plan EXPLAIN Plan etc

Some show you the real numbers SQL Monitor Reports and other Plan Statistics approaches

Only a optimizer trace file can truly show you why there is a discrepancy Sometimes ;-)

01/10/2013

Cost Based Oracle Fundamentals - Appendix Jonathan Lewis

http://tinyurl.com/bxxl6

Under the hood of the CBO Wolfgang Breitling


Using new 11g tracing infrastructure to generate files Optimizer Development Group (Maria Colgan)

http://tinyurl.com/brcryva and http://tinyurl.com/cr5kz8t

Greg Rahnhttp://tinyurl.com/bupmehx

01/10/2013



http://tinyurl.com/brcryva

http://tinyurl.com/cr5kz8t

http://tinyurl.com/bupmehx

My Blog Posts http://oracledoug.com

Recent Blog Post http://jonathanlewis.wordpress.com

Thanks Wolfgang Breitling

Maria Colgan & Greg Rahn

Jonathan Lewis

To you, for listening

01/10/2013

http://oracledoug.com/

http://jonathanlewis.wordpress.com/

Doug Burns [email protected]://oracledoug.com@orcldoug#OTW#OakTable

10053 otw

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