SQL Plan Management with Oracle Database provides tools to manage SQL performance and stability. It includes SQL profiles, stored outlines, SQL patches, and SQL baselines that can capture and enforce execution plans. New features in Oracle 12c include adaptive plans, which automatically choose join methods and parallel distribution, as well as adaptive statistics using dynamic sampling to improve cardinality estimates. Bind variable peeking and cardinality feedback also help the optimizer select optimal plans.

1. SQL Plan Management with
Oracle Database

2. Who Am I ?
Oracle OCP 12c
OCE 11g PT
OCE 11g RAC
Senior Specialist at RT Labs
The guy on the right ^_^

3. SPM
Stability
SQL Profiles
Stored
Outlines
SQL Patches SQL Baselines
Instability
Statistics
Cardinality
Feedback
Bind Variable
Peeking
Adaptive
Cursor Sharing
12 New
Features
Adaptive plans
Adaptive
statistics
Presentation plan

4. E-ROWS !=A-ROWS
• When estimated rows != actual rows
----------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows | Cost (%CPU)| A-Rows | A-Time | Buffers | Reads |
----------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | 1049 (100)| 0 |00:00:00.36 | 11000 | 6588 |
| 1 | NESTED LOOPS | | 1 | 100 | 1049 (3)| 0 |00:00:00.36 | 11000 | 6588 |
| 2 | NESTED LOOPS | | 1 | 100 | 1049 (3)| 2000 |00:00:00.35 | 9000 | 6552 |
|* 3 | TABLE ACCESS FULL | T1 | 1 | 100 | 849 (4)| 2000 |00:00:00.30 | 6554 | 6551 |
|* 4 | INDEX UNIQUE SCAN | T2_PK | 2000 | 1 | 1 (0)| 2000 |00:00:00.02 | 2446 | 1 |
|* 5 | TABLE ACCESS BY INDEX ROWID| T2 | 2000 | 1 | 2 (0)| 0 |00:00:00.01 | 2000 | 36 |
----------------------------------------------------------------------------------------------------------------------

5. Presentation plan
SPM
Stability
SQL Profiles
Stored
Outlines
SQL Patches SQL Baselines
Instability
Statistics
Cardinality
Feedback
Bind Variable
Peeking
Adaptive
Cursor Sharing
12 New
Features
Adaptive plans
Adaptive
statistics

6. SQL Profiles
• created by SQL Tunning Advisor
• enabled by default
• can be applied to multiple statements ( force_matching )
• using OPT_ESTIMATE hints
• invalid hints silently ignored
• has procedure to import hints ( import_sql_profile )
• uses categories (default by default )

7. Profiles, what is inside ?
OUTLINE_HINTS
------------------------------------------------------------------------------------------------------------
OPT_ESTIMATE(@"SEL$4C54F62B", NLJ_INDEX_FILTER, "THIS_"@"SEL$2", ("THIS_1_"@"SEL$2"), "FDC_LOT_PK",
SCALE_ROWS=0.4164795196)
OPT_ESTIMATE(@"SEL$4C54F62B", NLJ_INDEX_SCAN, "THIS_"@"SEL$2", ("THIS_1_"@"SEL$2"), "FDC_LOT_PK",
SCALE_ROWS=0.4164795196)
OPT_ESTIMATE(@"SEL$4C54F62B", NLJ_INDEX_FILTER, "THIS_1_"@"SEL$2", ("NOTIFICATI1_"@"SEL$3",
"THIS_"@"SEL$2", "P"@"SEL$7"), "FDC_LOT_SHARED_BASE_I", SCALE_ROWS=5.662569566e-06)
OPT_ESTIMATE(@"SEL$4C54F62B", JOIN, ("NOTIFICATI1_"@"SEL$3", "P"@"SEL$7"),
SCALE_ROWS=0.4236734421)
OPTIMIZER_FEATURES_ENABLE(default)
Wolfgang Breitling: Tunning by cardinality feedback

8. Presentation plan
SPM
Stability
SQL Profiles
Stored
Outlines
SQL Patches SQL Baselines
Instability
Statistics
Cardinality
Feedback
Bind Variable
Peeking
Adaptive
Cursor Sharing
12 New
Features
Adaptive plans
Adaptive
statistics

9. Stored Outlines
• not enabled in every session by default
• need to use use_stored_outlines=true
• Overrides (disables ) Profiles,Patches and Bselines
• need logon trigger to enable on startup
• invalid hints silently ignored
• work in 11c,12c but deprecated
• uses categories

10. Presentation plan
SPM
Stability
SQL Profiles
Stored
Outlines
SQL Patches SQL Baselines
Instability
Statistics
Cardinality
Feedback
Bind Variable
Peeking
Adaptive
Cursor Sharing
12 New
Features
Adaptive plans
Adaptive
statistics

11. SQL Patches
• Created by SQL Repair Advisor ( dbms_sqldiag )
• MOS Note 215187.1 SQLT has a script to generate manual SQL Profiles
• enabled by default
• No force matching
• Invalid hints silently ignored
• Can import hints
• dbms_sqldiag_internal.i_create_patch
• Capable of applying any valid hints
• Hints can be merged with Profiles and Baselines

12. Hints can be merged with Profiles and Baselines
SQL_ID c7q8y75rh36sc, child number 1
-------------------------------------
select /* test */ avg(pk_col) from skew where col1 = 23489
Plan hash value: 3723858078
------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 36 (100) | |
| 1 | SORTAGGREGATE | | 1 | 11 | | |
| 2 | TABLE ACCESS BY INDEX ROWID | SKEW | 35 | 385 | 36 (0) |00:00:01 |
|* 3 | INDEX RANGE SCAN | SKEW_COL1 | 37 | | 3 (0) |00:00:01 |
------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("COL1"=23489)
Note -----
- SQL profile PROF_c7q8y75rh36sc_3723858078 used for this statement
- SQL patch "KSO_c7q8y75rh36sc_MANUAL" used for this statement
- SQL plan baseline SQLID_C7Q8Y75RH36SC_3723858078 used for this statement

13. Presentation plan
SPM
Stability
SQL Profiles
Stored
Outlines
SQL Patches SQL Baselines
Instability
Statistics
Cardinality
Feedback
Bind Variable
Peeking
Adaptive
Cursor Sharing
12 New
Features
Adaptive plans
Adaptive
statistics

14. SQL Baselines
• Overriden by Outlines
• Provides procedure to import plans ( dbms_spm.load_plans_from_cursor_cache )
• Invalid hints NOT silently ignored
• Has associated plan_hash_value
• Capable to apply any valid hints
• Enabled by default
• Closer to outlines than to SQL Profiles
• Goal was to prevent performance regression
• Can have multiple Baselines per statement
• Can work with Profiles and Patches ( merges hints )
• Can be bulk loaded from
• Outlines
• SQL Tunning Set
• via optimizer_capture_sql_plan_baselines=true
• the cursor cache

15. What’s inside?
• A plan hash value
• hints to reproduce the plan
• Signature ( no sql_id )
SQL_PLAN_61c4s16v476sm308a34f6
NO HINTS
HINTS

16. Presentation plan
SPM
Stability
SQL Profiles
Stored
Outlines
SQL Patches SQL Baselines
Instability
Statistics
Cardinality
Feedback
Bind Variable
Peeking
Adaptive
Cursor Sharing
12 New
Features
Adaptive plans
Adaptive
statistics

17. Cardinality Feedback
• Was introduced in Oracle Database 11gR2
• Cardinality feedback monitoring may be enabled in the following
cases:
• tables with no statistics
• multiple conjunctive or disjunctive filter predicates on a table
• predicates containing complex operators that the optimizer cannot accurately
compute selectivity estimates for
• dynamic sampling or multi-column statistics allow the optimizer to more
accurately estimate selectivity of conjunctive predicates. In cases where
these techniques apply, cardinality feedback is not enabled.

18. @Desktop/Card_feedback_demo.sql

19. Presentation plan
SPM
Stability
SQL Profiles
Stored
Outlines
SQL Patches SQL Baselines
Instability
Statistics
Cardinality
Feedback
Bind Variable
Peeking
Adaptive
Cursor Sharing
12 New
Features
Adaptive plans
Adaptive
statistics

20. Bind Variable Peeking
Upgrade to 11g and let Adaptive Cursor Sharing take care of all your problems

21. Adaptive Cursor Sharing: Overview (Doc ID
740052.1)
SELECT child_number,
bucket_id,
count
FROM v$sql_cs_histogram
WHERE sql_id = '04pq01r0y8208'
ORDER BY child_number, bucket_id;
CHILD_NUMBER | BUCKET_ID | COUNT
------------ | ---------- | ----------
0 | 0 | 742
0 | 1 | 19
0 | 2 | 0
1 | 0 | 1031
1 | 1 | 51
1 | 2 | 0
2 | 0 | 1774
2 | 1 | 34
2 | 2 | 0
The first one (bucket_id equal 0) is associated
with the executions that are considered efficient
the second one (bucket_id equal 1) with the
executions that are considered inefficient
and the third one (bucket_id equal 2)
with the very inefficient executions

22. Adaptive Query Optimization
Adaptive
Plans
Join Methods
Parallel
Distribution
Methods
Adaptive
Statistics
Dynamic
Statistics
SQL Plan
Directives
12c New Features

23. Adaptive Query Optimization
Adaptive
Plans
Join Methods
Parallel
Distribution
Methods
Adaptive
Statistics
Dynamic
Statistics
SQL Plan
Directives
12c New Features

24. Join methods
• Nested Loops Joins
• Hash Joins
• Sort Merge Joins
• Cartesian Joins
• Purpose of Adaptive
Plans

25. How to find adaptive plans ?
• It’s easy
• select sql_id,child_number,substr ( replace(replace (sql_text,chr(10),' '),chr(13),' '),1,100)
text,IS_RESOLVED_ADAPTIVE_PLAN,IS_REOPTIMIZABLE from v$sql where IS_RESOLVED_ADAPTIVE_PLAN='Y';

26. Adaptive Query Optimization
Adaptive
Plans
Join Methods
Parallel
Distribution
Methods
Adaptive
Statistics
Dynamic
Statistics
SQL Plan
Directives
12c New Features

27. Adaptive Distribution Methods
• New adaptive distribution method HYBRID-HASH
• Statistic collectors inserted in front of PX process
• If actual number of rows less than threshold, switch from HASH to Broadcast
• Threshold number of total rows < 2xDOP
• Enabled by default
• If you want more read the articles of Randolf Geist ( link )

28. Adaptive Query Optimization
Adaptive
Plans
Join Methods
Parallel
Distribution
Methods
Adaptive
Statistics
Dynamic
Statistics
SQL Plan
Directives
12c New Features

29. Optimizer Dynamic Statistics (OPTIMIZER_DYNAMIC_SAMPLING)
(Doc ID 336267.1)
Level When Optimizer Uses Dynamic Statistis Sample Size (
blocks )
0 Do not use dynamic statistics 0
1 Use dynamic statistics for all tables that do not have statistics, but only if the
following criteria are met: There is at least 1 non partitioned table in the query that
does not have statistics. This table has no indexes. This table has more blocks than
the number of blocks that would be used for dynamic statistics of this table.
32
2 Use dynamic statistics if at least one table in the statement has no statistics. This is
the default setting.
64
3 As per Level 2, plus all tables for which standard selectivity estimates used a guess
for some predicate that is a potential dynamic sampling predicate.
64
4 As per Level 3, plus all tables that have complex predicate expressions (for example
single-table predicates that reference 2 or more columns or non-equality where
clause predicates on two correlated columns).
64
5 As per Level 4 with a larger sample size each time. 128
6 As per Level 4 with a larger sample size each time. 256
7 As per Level 4 with a larger sample size each time. 512
8 As per Level 4 with a larger sample size each time. 1024
9 As per Level 4 with a larger sample size each time. 4096
10 Use dynamic sampling for all statements sampling All blocks All
11 (11gR2 11.2.0.4 and above) The Optimizer will automatically decide if dynamic
statistics will be useful, and what dynamic sampling level will be used for SQL
statements.
Automagical
stuff

30. Dynamic statistics 12c version. What’s New
• Join statistics are monitored
• Works with adaptive cursor sharing for statement with binds
• New Column in V$SQL IS_REOPTIMIZABLE
• Information found at execution time is persisted as SQL Plan
Directives
• Dynamic statistics (Doc ID 2002108.1)

31. Adaptive Query Optimization
Adaptive
Plans
Join Methods
Parallel
Distribution
Methods
Adaptive
Statistics
Dynamic
Statistics
SQL Plan
Directives
12c New Features

32. SQL Plan Directives
What was already there in 11g :
• Cardinality feedback
• Estimated cardinalities are checked at execution time
• Actual cardinalities are stored with cursor for future re-optimization
• Not persistent
• Extended statistics
• Gathers statistics on group of columns, or functions
• Defined manually or from through ‘seed column usage’
• Dynamic sampling

33. SQL Plan Directives
A 12c new features
sql plan directive might instruct the optimizer to :
• Collect missing statistics
• Create column group statistics
• Perform dynamic statistics (Dynamic Sampling).
• Only when we know that more statistics can help
• SPD is created when statement is marked as reoptimizable

34. SPD Persistent
• In memory
• Are not used by optimizer when only in memory (shared pool)
• Are not exported when only in memory: must flush before
• Flushed every 15 minutes
• Stored in SYSAUX
• Flushed manually
• exec dbms_spd.flush_sql_plan_directive;

35. SQL Plan Directives States Internal States
NEW
MiSSING STATS
HAS STATS
PERMANENT
Statement reoptimizable
Dynamic sampling
Extented stats
misestimates
good estimation

36. SPD_TEXT
• Additional information dba_sql_plan_directives
Description Notation
equality_predicates_only E (SCHEMA.TABLE) [COL, COL]
simple_column_predicates_only C (SCHEMA.TABLE) [COL, COL]
index_access_by_join_predicates J (SCHEMA.TABLE) [COL, COL]
filter_on_joining_object F (SCHEMA.TABLE) [COL, COL]

37. @Desktop/SPD_demo.sql

38. Summarize changes in terminology
• Adaptive Optimization – any dynamic change to plan
• Adaptive Plans – changed from default on 1st execution
• Automatic Re-optimization – 2nd execution
• Statistics Feedback = Cardinality Feedback
• Dynamic Statistics = Dynamic Sampling
• SQL Plan Directives = Persisted Dynamic Sampling (for now)

39. Scary slide for those who want to upgrade
wright now

40. All of this features have some overhead
• parameter recommendations for oracle database 12c part 1
• parameter recommendations for oracle database 12c part2
• https://iusoltsev.wordpress.com/2016/02/18/12c-automatic-
dynamic-sampling/
• https://iusoltsev.wordpress.com/2016/02/18/12c-automatic-
dynamic-sampling/

41. Plus Knows bugs:
• NOTE:20978266.8 — Bug 20978266 — SQL not using plan in plan baselines and plans showing as
not reproducible — superseded
• NOTE:21075138.8 — Bug 21075138 — SPM does not reproduce plan with SORT UNIQUE
• NOTE:21463894.8 — Bug 21463894 — Failure to reproduce plan with fix for bug 20978266
• NOTE:19141838.8 — Bug 19141838 — ORA-600 [qksanGetTextStr:1] from SQL Plan Management
after Upgrade to 12.1
• NOTE:18961555.8 — Bug 18961555 — Static PL/SQL baseline reproduction broken by fix for bug
18020394
• NOTE:18747342.8 — Bug 18747342 — Plan reproduction fails for SQL statement with a [NOT]
EXISTS select list subquery

42. Adaptive optimisation controls
• optimizer_adaptive_features = false
• big switch - controls all adaptive stuff
• optimizer_features_enable <= 12.1.0.1
• even bigger switch – please don’t use this one!
• optimizer_adaptive_reporting_only = true
• _optimizer_adaptive_plans=false
• individual control for adaptive plans
• optimizer_dynamic_sampling=0
• individual control for dynamic sampling
• _optimizer_use_feedback=false
• individual control for cardinality feedback

43. Used materials:
• White Papers and Blog Entries for Oracle Optimizer (Doc ID
1337116.1)
• 12c Adaptive Optimization - Kerry Osborne
• Articles of Franck Pachot
• Articles of Igor Usoltsev

44. Questions ?
Mail_to:bushmelev.aa@gmail.com