Presentation for DBA Brasil 2.0

1. Oracle
SQL Tuning 101
Alex Zaballa, Accenture Enkitec Group

3. Alex Zaballa
http://alexzaballa.blogspot.com/
@alexzaballa
https://www.linkedin.com/in/alexzaballa
Worked for 3 years as a Clipper/Delphi Developer (15 years old)
Worked for 7 years in Brazil as an Oracle Developer.
Worked 8 years for the Ministry of Finance
In Angola as a DBA
March - 2007 until March - 2015*

5. TUNING
e não
TANING

6. Oracle Database
Enterprise Edition +
Diagnostics Pack +
Tuning Pack
*

7. Database Tuning
Vs
SQL Tuning
*

8. Desenvolvedores
vs
SQL
*

9. •Aplicações multi-banco
•ORM : Object Relational
Mapper

10. ”The Oracle optimizer uses
the constraints to make
better decisions on join
paths.”

11. Cost of an Index
FKs **
In-Memory**
*

12. Nada mudou e hoje a
aplicação está lenta!

13. Mudanças que podem trazer
problemas
• Database upgraded
• Statistics gathered
• Schema changed
• Database parameter changed
• Application changed
• Operating system (OS) and hardware changed
• Data volume changed by more active users

14. Ferramentas para SQL Tuning -
Oracle
• SQL Trace (and TKPROF)
• Active Session History (ASH)
• EXPLAIN PLAN FOR
• AUTOTRACE
• SQL Developer
• DBMS_XPLAN
• SQL Monitor

15. ASH e AWR
• 1 sec snapshots of V$SESSION into ASH
• Every 10 ASH samples into AWR
**Requires Oracle Diagnostics Pack
*

16. Tom Kyte

17. Tipos de SQL Tuning
Proativo

18. Tipos de SQL Tuning
Reativo
*

19. Proativo

20. eDB360
*

21. Top SQLs
*

22. Top Events

23. AWR
• SQL ordered by Elapsed Time
• SQL ordered by CPU Time
• SQL ordered by User I/O Wait Time
• SQL ordered by Gets
• SQL ordered by Reads
• SQL ordered by Physical Reads (UnOptimized)
• SQL ordered by Executions
• SQL ordered by Parse Calls
• SQL ordered by Sharable Memory
• SQL ordered by Version Count
• SQL ordered by Cluster Wait Time*

24. SQL ordered by Elapsed Time

25. SQL ordered by Executions - RAC

26. Reativo

27. *

28. Reativo - SQLT Diagnostic Tool
(Doc ID 215187.1)
• Prós: Suportada e atualizada pela Oracle
• Contras: Necessário instalação
Criada pelo Carlos Sierra
*

30. Reativo - SQLD360
Criada pelo Mauro Pagano
*

31. Reativo - SQLD360

32. Reativo - SQLD360

33. Explain Plan?

34. Explain Plan
Apenas tenta prever o plano que será executado!

35. Explain Plan
• Bind Variable Peeking
• Adaptive Features
• Etc

36. Now what?
• DBMS_XPLAN.DISPLAY_CURSOR
• V$SQL_PLAN%

37. DBMS_XPLAN.DISPLAY_CURSOR
• SQL_ID
• CURSOR_CHILD_NO (default 0)
• FORMAT
§ TYPICAL = DEFAULT
§ ALL = TYPICAL + QB + PROJECTION + ALIAS + REMOTE
§ ADVANCED = ALL + OUTLINE + BINDS
§ ALLSTATS = IOSTATS + MEMSTATS (all executions)
§ ALLSTATS LAST (last execution)
§ ADAPTIVE (12c)

38. DBMS_XPLAN
• DISPLAY (from PLAN_TABLE)
• DISPLAY_CURSOR
• DISPLAY_AWR
• DISPLAY_SQL_PLAN_BASELINE
• DISPLAY_SQL_SET
SELECT * FROM
TABLE(DBMS_XPLAN.DISPLAY_CURSOR('sql_id',child,'ADVANCED'));

39. By Carlos Sierra

40. Estimate vs Actual
https://blogs.oracle.com/optimizer/entry/how_do_i_know_if
/*+ gather_plan_statistics */
or
Alter session set statistics_level = ALL

41. SQL MONITOR
• Real-time SQL monitoring foi introduzido no
Oracle Database 11g.
• Parallel queries, DML e DDL são
automaticamente monitorados.
• SQLs que consumem 5 segundos ou mais
segundos de CPU ou I/O em uma única
execução
• Hint /*+ MONITOR */

42. SQL MONITOR
• Oracle Enterprise Manager
• EM Database Express (12c)
• SQL Developer
• Linha de Comando
**Part of the Oracle Tuning Pack

43. SQL MONITOR
select dbms_sqltune.report_sql_monitor(
sql_id => 'gjabwvvr07w09',
report_level=>'ALL',
type => 'ACTIVE') from dual;

44. SQL MONITOR

45. SQL MONITOR

46. Evento 10053
Mais conhecido como ”Wolfganging”
” Wolfgang Breitling was the first guy to really
analyze the content of these 10053 trace files
and publish his findings.”
Wolfgang wrote a paper called “A Look
Under the Hood of CBO.”

47. Evento 10053
ALTER SESSION SET EVENTS '10053 trace name
context forever, level 1';
SELECT * FROM EMP WHERE ENAME = 'SCOTT';
ALTER SESSION SET EVENTS '10053 trace name
context off';

48. Evento 10053
Level 1 or Level 2?
• 1. Parameters used by the optimizer (level 1 only)
• 2. Index statistics (level 1 only)
• 3. Column statistics
• 4. Single Access Paths
• 5. Join Costs
• 6. Table Joins Considered
• 7. Join Methods Considered (NL/MS/HA)

49. Evento 10053
For another session:
SYS.DBMS_SYSTEM.SET_EV (SID,SERIAL ,10053,1)
Disable:
SYS.DBMS_SYSTEM.SET_EV (SID,SERIAL ,10053,0)

50. Evento 10053
11G R1 – SQL Inside PL/SQL
ALTER SESSION SET EVENTS
'trace[rdbms.SQL_Optimizer.*][sql:my_sql_id]';
ALTER SESSION SET EVENTS
'trace[rdbms.SQL_Optimizer.*] off';

51. Evento 10053
11G R2
dbms_sqldiag.dump_trace(
p_sql_id=>’92c3fw9svc3rc’,
p_child_number=>0,
p_component=>'Compiler',
p_file_id=>’MY_Trace_File');
** Doesn’t require you to re-execute the statement.

52. Evento 10053

53. Evento 10053
ALTER SESSION SET EVENTS '10053 trace name
context forever, level 1';
SELECT * FROM tb_pai p
WHERE EXISTS (SELECT 1 FROM tb_filho f
WHERE f.id_pai=p.id);
ALTER SESSION SET EVENTS '10053 trace name
context off';

54. Evento 10053

55. Evento 10053

56. Evento 10053
QUERY BLOCK – 2 partes da query

57. Evento 10053
Paralelismo desabilitado

58. Evento 10053

59. Evento 10053

60. Evento 10053
System Statistics

61. Evento 10053
Sem Estatísticas

62. Evento 10053
Dynamic Sampling

63. Evento 10053
Table Scan – Sem Índices

64. Evento 10053
Best Join Order

65. Evento 10053

66. Evento 10053

67. Evento 10053
Exemplo 2

68. Evento 10053

69. Evento 10053

70. OR Expansion
Query Original:
SELECT * FROM emp
WHERE job = 'CLERK' OR deptno = 10;
Query Transformada:
SELECT * FROM emp
WHERE job = 'CLERK’
UNION ALL
SELECT * FROM emp
WHERE deptno = 10 AND job <> 'CLERK';

71. Subquery Unnesting
Query Original:
SELECT * FROM accounts
WHERE custno IN
(SELECT custno FROM customers);
Query Transformada:
SELECT accounts.*
FROM accounts, customers
WHERE accounts.custno = customers.custno;

72. View Merging
Query Original:
CREATE VIEW emp_10 AS
SELECT empno, ename, job, sal, comm, deptno
FROM emp
WHERE deptno = 10;
SELECT empno FROM emp_10
WHERE empno > 7800;
Query transformada:
SELECT empno
FROM emp
WHERE deptno = 10 AND empno > 7800;

73. Predicate Pushing
Query Original:
CREATE VIEW two_emp_tables AS
SELECT empno, ename, job, sal, comm, deptno
FROM emp1
UNION
SELECT empno, ename, job, sal, comm, deptno
FROM emp2;
SELECT ename FROM two_emp_tables
WHERE deptno = 20;

74. Predicate Pushing
Query Transformada:
SELECT ename
FROM ( SELECT empno, ename, job,sal, comm, deptno
FROM emp1 WHERE deptno = 20
UNION
SELECT empno, ename, job,sal, comm, deptno
FROM emp2 WHERE deptno = 20 );

75. Transitivity
Query Original:
SELECT *
FROM emp, dept
WHERE emp.deptno = 20
AND emp.deptno = dept.deptno;
Query Transformada:
SELECT *
FROM emp, dept
WHERE emp.deptno = 20
AND emp.deptno = dept.deptno
AND dept.deptno = 20;

76. Evento 10053

77. Full Table Scan
https://www.slideshare.net/MauroPagano3/
full-table-scan-friend-or-foe
*

78. Full Table Scan
https://www.slideshare.net/MauroPagano3/
full-table-scan-friend-or-foe

79. Full Table Scan
https://richardfoote.wordpress.com/2008/05/12/index-scan-
or-full-table-scan-the-magic-number-magic-dance/
*

80. Full Table Scan
• Clustering Factor --> How well ordered the
rows in the table are in relation to the index.
• Selectivity of the query
• Number of table blocks
• Effective multiblock read count
• Relative cost of single vs. multiblock I/Os
• Parallelism
• Etc

81. Full Table Scan
https://www.slideshare.net/MauroPagano3/
full-table-scan-friend-or-foe

82. Full Table Scan

83. Adaptive Features
Oracle Database 12.1
• OPTIMIZER_ADAPTIVE_FEATURES
Default TRUE

84. Adaptive Features
Oracle Database 12.2 introduces the new
split-up adaptive parameters:
• OPTIMIZER_ADAPTIVE_PLANS
• OPTIMITER_ADAPTIVE_STATISTICS.

85. Adaptive Features
• On Oracle Database 12.1this can be
achieved by installing two patches.

86. Adaptive Features
The patch for bug# 22652097 introduces the two parameters
OPTIMIZER_ADAPTIVE_PLANS and
OPTIMIZER_ADAPTIVE_STATISTICS, and in addition removes
the parameter OPTIMIZER_ADAPTIVE_FEATURES.
The patch for bug# 21171382 disables the automatic creation
of extended statistics unless the optimizer preference
AUTO_STATS_EXTENSIONS is set to ON.

87. Statistics
https://blogs.oracle.com/optimizer/entry/improvement_of_auto_sampling_statistics
_gathering_feature_in_oracle_database_11g
estimate_percent => dbms_stats.auto_sample_size

88. Hints
• Devo utilizar ?
• O desenvolvedores/dbas sabem mais que
o otimizador?

89. Hints
• Use para fornecer dados ao otimizador
que as estatísticas falharam em informar;
• Use com precaução;
• Use como último recurso.

90. SQL Tuning on EXADATA
• Tempo da query na M7: 180 minutos
• Tempo após clone - P8+Storage ?
• Tempo após ajuste da query: 29 horas
• Tempos após ajuste no M7: 17 minutos

91. SQL Tuning on EXADATA

93. Pending Statistics
Set table preferences:
begin
dbms_stats.set_table_prefs (
ownname => 'SCOTT',
tabname => 'EMP',
pname => 'PUBLISH',
pvalue => 'FALSE'
);
end;
Collect the statistics.

94. Pending Statistics
select num_rows,
to_char(last_analyzed,'dd/mm/rrrr hh24:mi:ss')
from all_tab_pending_stats
where table_name = 'EMP';

95. Pending Statistics
alter session set
optimizer_use_pending_statistics = true;
Test the queries.

96. Pending Statistics
If it’s ok:
dbms_stats.publish_pending_stats('SCOTT',
'EMP');
or:
dbms_stats.delete_pending_stats(’SCOTT',
’EMP');

97. Restore Statistics from History
Check the retention:
select
DBMS_STATS.GET_STATS_HISTORY_RETENTI
ON from dual;
Default is 31 days.

98. Restore Statistics from History
Statistics available for the table:
SELECT OWNER,
TABLE_NAME,
STATS_UPDATE_TIME
FROM dba_tab_stats_history
WHERE table_name='MY_TABLE';

99. Restore Statistics from History
Begin
dbms_stats.restore_table_stats(
'SCOTT',
'EMP',
‘08-NOV-16 11.38.05.015640 AM +08:00’);
End;

100. Export and Import schema
statistics
begin
dbms_stats.CREATE_STAT_TABLE( ownname=>user
, stattab=>'MY_STATS_TABLE'
);
end;
begin
dbms_stats.export_schema_stats( ownname=>user
, stattab=>'MY_STATS_TABLE'
, statid=>'CURRENT_STATS'
);
End;

101. Export and Import schema
statistics
EXPDP / IMPDP
begin
dbms_stats.import_schema_stats( ownname=>user
, stattab=>'MY_STATS_TABLE'
, statid=>'CURRENT_STATS'
);
End;

102. Incremental Statistics
Estatísticas incrementais para Tabelas
Particionadas:
dbms_stats.set_table_prefs(null,'SALES'
,'INCREMENTAL','TRUE')
11g**

103. Incremental Statistics

104. Invisible Indexes
• CREATE INDEX index_name ON
table_name(column_name) INVISIBLE;
• ALTER INDEX index_name INVISIBLE;
• ALTER INDEX index_name VISIBLE;

105. Invisible Indexes
ALTER SESSION SET
OPTIMIZER_USE_INVISIBLE_INDEXES=TRUE;

106. Row-by-Row Processing vs Bulk
Processing
Instead of fetching a single row at a time
it is possible to use the bulk features.

107. Row-by-Row Processing vs Bulk
Processing

108. Row-by-Row Processing vs Bulk
Processing
*

109. SQL trace, 10046, trcsess and
tkprof
ALTER SESSION SET sql_trace=TRUE;
ALTER SESSION SET sql_trace=FALSE;
EXEC DBMS_SESSION.set_sql_trace(sql_trace => TRUE);
EXEC DBMS_SESSION.set_sql_trace(sql_trace => FALSE);
ALTER SESSION SET EVENTS '10046 trace name context forever, level 12';
ALTER SESSION SET EVENTS '10046 trace name context off';
EXEC DBMS_SYSTEM.set_sql_trace_in_session(sid=>0000, serial#=>0000, sql_trace=>TRUE);
EXEC DBMS_SYSTEM.set_sql_trace_in_session(sid=>0000, serial#=>0000, sql_trace=>FALSE);

110. SQL trace, 10046, trcsess and
tkprof
CONN sys/password AS SYSDBA;
ORADEBUG SETMYPID;
ORADEBUG SETOSPID 0000;
ORADEBUG SETORAPID 000000;
ORADEBUG EVENT 10046 TRACE NAME CONTEXT FOREVER, LEVEL 12;
ORADEBUG EVENT 10046 TRACE NAME CONTEXT OFF;

111. SQL trace, 10046, trcsess and
tkprof
EXEC DBMS_SUPPORT.start_trace(waits=>TRUE, binds=>TRUE);
EXEC DBMS_SUPPORT.stop_trace;
EXEC DBMS_SUPPORT.start_trace_in_session(sid=>0000, serial=>000000,
waits=>TRUE, binds=>TRUE);
EXEC DBMS_SUPPORT.stop_trace_in_session(sid=>0000, serial=>000000);

112. SQL trace, 10046, trcsess and
tkprof
10g:
DBMS_MONITOR.session_trace_enable(waits=>TRUE, binds=>FALSE);
DBMS_MONITOR.session_trace_enable(session_id =>0000, serial_num=>000000,
waits=>TRUE, binds=>TRUE);
DBMS_MONITOR.client_id_trace_enable(client_id=>'my_client', waits=>TRUE,
binds=>TRUE);
DBMS_MONITOR.serv_mod_act_trace_enable(service_name=>'my_srv',
module_name=>'my_test', action_name=>'calculating', waits=>TRUE, binds=>TRUE);

113. SQL trace, 10046, trcsess and
tkprof
ALTER SESSION SET TRACEFILE_IDENTIFIER =
"MY_TRC_FILE";

114. SQL trace, 10046, trcsess and
tkprof
SELECT p.tracefile
FROM v$session s
JOIN v$process p
ON s.paddr = p.addr
WHERE s.sid = MY_SID;

115. SQL trace, 10046, trcsess and
tkprof
12.2
v$diag_trace_file
v$diag_trace_file_contents

116. Evento 10046

117. Evento 10046
ALTER SESSION SET EVENTS '10046 trace name
context forever, level 12';
SELECT * FROM tb_pai p
WHERE EXISTS (SELECT 1 FROM tb_filho f
WHERE f.id_pai=p.id);
ALTER SESSION SET EVENTS '10046 trace name
context off';

118. Evento 10046

119. Evento 10046

120. Evento 10046

121. Evento 10046

122. Evento 10046

123. Evento 10046

124. SQL trace, 10046, trcsess and
tkprof
• TKPROF
• TRCSESS
• Trace Analyzer TRCANLZR (TRCA)
• Method R Tools

125. SQL trace, 10046, trcsess and
tkprof

126. SQL trace, 10046, trcsess and
tkprof
http://www.oraclenerd.com/2011/02/sql-developer-mr-trace.html

127. Questions?

128. Thank You
Slides Available: http://www.slideshare.net/