10053 otw

Doug Burns dougburns@yahoo.com
http://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

 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

 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

 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

 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
*******************************************

 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

 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

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

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
*/

 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
http://tinyurl.com/bxxl6
 Using new 11g tracing infrastructure to generate files
 Optimizer Development Group (Maria Colgan)
http://tinyurl.com/brcryva and http://tinyurl.com/cr5kz8t
 Greg Rahn
http://tinyurl.com/bupmehx
01/10/2013

 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

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