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Dbms plan - A swiss army knife for performance engineers

This document discusses dbms_xplan, a tool for performance engineers to analyze execution plans. It provides options for displaying plans from the plan table, shared SQL area in memory, and AWR history. Dbms_xplan provides more detailed information than traditional tools like tkprof, including predicates, notes, bind values, and plan history. It requires privileges to access dictionary views for displaying plans from memory and AWR. The document also demonstrates usage examples and output formats for dbms_xplan.analyze.

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dbms_xplan: A Swiss army knife for performance engineers Sahil Thapar Riyaj Shamsudeen
2 Disclaimer These slides and materials represent the work and opinions of the author and do not constitute official positions of my current or past employer or any other organization. This material has been peer reviewed, but author assume no responsibility whatsoever for the test cases. If you corrupt your databases by running my scripts, you are solely responsible for that.
3 Options EXPLAIN PLAN (Version 7 or older) AUTOTRACE ( Version 8i +) SQL_TRACE (Version 7) DBMS_XPLAN Estimated, not always reliable Actual plan, buggy. Actual plan; but must enable trace before the run. Actual plan, after the run, always available.
PARSING IN CURSOR #1844674 len=1000 dep=0 uid=173 oct=3 lid=173 tim=7861072491388 hv=2701626457 ad='498d8f1d0' sqlid='9sup9gfhhg32t' SELECT RECID, TABLENAME, PROJECT_NUMBER, PROJECT_NAME, CARRYING_OUT_ORGANIZATION, ...FROM ( SELECT STGTBL_RECID ... WHERE PROCESSED_FLAG='U' ) ORDER BY TABLENAME, CREATION_DATE PARSE:#1844674:c=10000,e=10162,p=0,cr=0,cu=0,mis=1,r=0,dep=0,og=1,plh=3298327531,tim=78610 72491386 EXEC:#1844674:c=0,e=139,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=3298327531,tim=786107249172 3 EXEC:#1844674:c=0,e=139,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=3298327531,tim=786107249172 3 .. WAIT #1844674: nam='Disk file operations I/O' ela= 2013 FileOperation=2 fileno=811 filetype=2 obj#=706379 tim=786107 FETCH#1844674:c=18020000,e=59603730,p=199262,cr=199331,cu=0,mis=0,r=0,dep=0,og=1,plh=32983 27531,tim=7861 … STAT #1844674 id=3 cnt=0 pid=2 pos=1 obj=0 op='SORT UNIQUE (cr=199331 pr=199262 pw=0 time=59603707 us cost=56817 size=126622640 card=2146146)' STAT #1844674 id=4 cnt=0 pid=3 pos=1 obj=0 op='UNION-ALL (cr=199331 pr=199262 pw=0 time=59603638 us)' 4 Raw trace file Content of a sql trace file:
5 tkprof (1) SELECT RECID, TABLENAME, PROJECT_NUMBER, PROJECT_NAME, CARRYING_OUT_ORGANIZATION, COMPANY, CHARGEABLE_FLAG, START_DATE, END_DATE, CREATION_DATE, LAST_UPDATE_DATE, PROCESSED_FLAG, ………………………………. …………………………….. WHERE PROCESSED_FLAG='U' ) ORDER BY TABLENAME, CREATION_DATE call count cpu elapsed disk query current rows ------- ------ -------- ---------- ---------- ---------- ---------- ---------- Parse 1 0.01 0.01 0 0 0 0 Execute 1 0.00 0.00 0 0 0 0 Fetch 1 18.02 59.60 199262 199331 0 0 ------- ------ -------- ---------- ---------- ---------- ---------- ---------- total 3 18.03 59.61 199262 199331 0 0
6 tkprof (2) Rows (max) Row Source Operation ---------- --------------------------------------------------- 0 SORT ORDER BY (cr=199331 pr=199262 pw=0 time=59603767 us cost=180933 size=641697654 card=2146146) 0 VIEW (cr=199331 pr=199262 pw=0 time=59603722 us cost=56817 size=641697654 card=2146146) 0 SORT UNIQUE (cr=199331 pr=199262 pw=0 time=59603707 us cost=56817 size=126622640 card=2146146) 0 UNION-ALL (cr=199331 pr=199262 pw=0 time=59603638 us) 0 TABLE ACCESS FULL ORD_AP_IF_PROJECTS (cr=46025 pr=45963 pw=0 time=17088312 us cost=6568 size=85 card=1) 0 TABLE ACCESS FULL ORD_AP_IF_TASKS (cr=153306 pr=153299 pw=0 time=42515291 us cost=21894 size=126622555 Elapsed times include waiting on following events: Event waited on Times Max. Wait Total Waited ---------------------------------------- Waited ---------- ------------ SQL*Net message to client 1 0.00 0.00 Disk file operations I/O 129 0.01 0.26
7 Usage  Displays execution plan stored in three different places 1) PLAN_TABLE dbms_xplan.diplay (estimated plan) 2) SGA of instance dbms_xplan.display_cursor (real plan from memory) 3) AWR dbms_xplan.display_awr (real,history plan from AWR)
8 Comparison Sl Tkprof Dbms_xplan 1 Trace must be enabled. Basic statistics are available in memory and AWR 2 CBO notes are not visible Note section is very useful 3 No predicate Predicates printed from memory. 4 Bind values can be retrieved with ease 5 Plan history can be retrieved easily.
select * from table(dbms_xplan.display_cursor(‘sql_id’,child_number,’format’)); 9 dbms_xplan format arguments Format Examples: select * from table( dbms_xplan.display_cursor()); select * from table ( dbms_xplan.display_cursor (null,null, 'ADVANCED')); select * from table ( dbms_xplan.display_cursor ('811a0zb26fw0x',0, 'BASIC')); select * from table ( dbms_xplan.display_cursor ('811a0zb26fw0x',0, ‘ALL -projection')); select * from table ( dbms_xplan.display_cursor ('811a0zb26fw0x',0, ‘ALL +peeked_binds')); Format arguments: ' ADVANCED' ' –PREDICATE' ' –PREDICATE +OUTLINE' TYPICAL is the default class Format arguments combination: Class level alias bytes cost note predicate parallel partition projection outlines peeked_binds remote rows BASIC null X X X X X TYPICAL X X X X X X X X SERIAL X X X X X X ALL X X X X X X X X X X X ADVANCED X X X X X X X X X X X X
SQL_ID 9sup9gfhhg32t, child number 0 ------------------------------------- SELECT RECID, TABLENAME, PROJECT_NUMBER, PROJECT_NAME, ……………………………………………………………………………………………L EDIT_CLASS_CODE, ALC, FRC FROM CCW_PA_IF_TASKS WHERE PROCESSED_FLAG='U' ) ORDER BY TABLENAME, CREATION_DATE Plan hash value: 3298327531 --------------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes |TempSpc| Cost (%CPU)| Time | ---------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | | | | 180K(100)| | | 1 | SORT ORDER BY | | 2146K| 611M| 698M| 180K (5)| 00:09:03 | | 2 | VIEW | | 2146K| 611M| | 56817 (10)| 00:02:51 | | 3 | SORT UNIQUE | | 2146K| 120M| 172M| 56817 (91)| 00:02:51 | | 4 | UNION-ALL | | | | | | | |* 5 | TABLE ACCESS FULL| ORD_AP_IF_PROJECTS | 1 | 85 | | 6568 (14)| 00:00:20 | |* 6 | TABLE ACCESS FULL| ORD_AP_IF_TASKS | 2146K| 120M| | 21894 (14)| 00:01:06 | ---------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 5 - filter("PROCESSED_FLAG"='U') 6 - filter("PROCESSED_FLAG"='U') Note ----- - SQL profile not used for this statement 10 dbms_xplan.display Optimizer estimates
11 Display_cursor select * from table(dbms_xplan.display_cursor('9yx90c0nwv9tk',0,'allstats')); SQL_ID 9yx90c0nwv9tk, child number 0 ------------------------------------- SELECT /* gather_plan_statistics */ RECID, TABLENAME, ... Plan hash value: 3298327531 --------------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | Reads | --------------------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 0 |00:00:32.50 | 199K| 199K| | 1 | SORT ORDER BY | | 1 | 2146K| 0 |00:00:32.50 | 199K| 199K| | 2 | VIEW | | 1 | 2146K| 0 |00:00:32.50 | 199K| 199K| | 3 | SORT UNIQUE | | 1 | 2146K| 0 |00:00:32.50 | 199K| 199K| | 4 | UNION-ALL | | 1 | | 0 |00:00:32.50 | 199K| 199K| |* 5 | TABLE ACCESS FULL| ORD_AP_IF_PROJECTS | 1 | 1 | 0 |00:00:07.90 | 46025 | 45963 | |* 6 | TABLE ACCESS FULL| ORD_AP_IF_TASKS | 1 | 2146K| 0 |00:00:24.60 | 153K| 153K| --------------------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 5 - filter("PROCESSED_FLAG"='U') 6 - filter("PROCESSED_FLAG"='U') Note, output formatted to fit screen
12 Easily quantify the solution given.. select * from table(dbms_xplan.display_cursor('9yx90c0nwv9tk',0,'allstats')); Plan hash value: 932773089 ---------------------------------------------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | OMem | 1Mem | Used-Mem | ---------------------------------------------------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 0 |00:00:00.01 | 6 | | | | | 1 | SORT ORDER BY | | 1 | 2146K| 0 |00:00:00.01 | 6 | 1024 | 1024 | | | 2 | VIEW | | 1 | 2146K| 0 |00:00:00.01 | 6 | | | | | 3 | SORT UNIQUE | | 1 | 2146K| 0 |00:00:00.01 | 6 | 1024 | 1024 | | | 4 | UNION-ALL | | 1 | | 0 |00:00:00.01 | 6 | | | | | 5 | TABLE ACCESS BY INDEX ROWID| ORD_PA_IF_PROJECTS | 1 | 1 | 0 |00:00:00.01 | 3 | | | | |* 6 | INDEX RANGE SCAN | ORD_PA_IF_PROJECTS_N1 | 1 | 1 | 0 |00:00:00.01 | 3 | | | | | 7 | TABLE ACCESS BY INDEX ROWID| ORD_PA_IF_TASKS | 1 | 2146K| 0 |00:00:00.01 | 3 | | | | |* 8 | INDEX RANGE SCAN | ORD_PA_IF_TASKS_N1 | 1 | 2173K| 0 |00:00:00.01 | 3 | | | | ---------------------------------------------------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 6 - access("PROCESSED_FLAG"='U') 8 - access("PROCESSED_FLAG"='U') Note -----
13 Privileges  Privileges needed to execute dbms_xplan For dbms_xplan.display_cursor grant select on v_$session to scott; grant select on v_$SQL_PLAN_STATISTICS_ALL to scott; grant select on v_$sql to scott; grant select on v_$sql_plan to scott; OR SELECT_CATALOG role or select any dictionary system privilege For dbms_xplan.display_awr grant select on dba_hist_sqltext to scott grant select on dba_hist_sql_plan to scott; grant select on v_$database to scott; OR SELECT_CATALOG role
Really complicated recursive SQL statements! 14 Internals of dbms_xplan select * from (table(dbms_xplan.display_cursor('8gzkcsvw362s3',2,'allstats')); select /* EXEC_FROM_DBMS_XPLAN */ case when upper(sql_text) like '%DBMS_XPLAN%' then 0 else 1 end case, SQL_ID, child_number from v$sql where SQL_ID ='8gzkcsvw362s3' and child_number =2 SELECT PLAN_TABLE_OUTPUT FROM TABLE(CAST(DBMS_XPLAN.PREPARE_RECORDS(:B1 , :B2 ) AS SYS.DBMS_XPLAN_TYPE_TABLE)) SELECT /*+ opt_param('parallel_execution_enabled', 'false') */ extractvalue(xmlval, '/*/info[@type = "sql_profile"]'), extractvalue(xmlval, '/*/info[@type = "sql_patch"]'), extractvalue(xmlval, '/*/info[@type = "baseline"]'), extractvalue(xmlval, '/*/info[@type = "outline"]'), extractvalue(xmlval, '/*/info[@type = "dynamic_sampling"]'), extractvalue(xmlval, '/*/info[@type = "dop"]'), extractvalue(xmlval, '/*/info[@type = "dop_reason"]'), extractvalue(xmlval, '/*/info[@type = "queuing_reason"]'), extractvalue(xmlval, '/*/info[@type = "row_shipping"]') , extractvalue(xmlval, '/*/info[@type = "index_size"]'), extractvalue(xmlval, '/*/info[@type = "result_checksum"]'), extractvalue(xmlval, '/*/info[@type = "cardinality_feedback"]'), extractvalue(xmlval, '/*/info[@type = "xml_suboptimal"]'), extractvalue(xmlval,'/*/info[@type = "plan_hash"]') from (select xmltype(:v_other_xml) xmlval from dual)
15 More internals SELECT /*+ opt_param('parallel_execution_enabled', 'false') */ /* EXEC_FROM_DBMS_XPLAN */ id, position, depth , operation, options, object_name, cardinality, bytes, temp_space, cost, io_cost, cpu_cost, time, …. vp.optimal_executions opt_cnt, vp.onepass_executions one_cnt, vp.multipasses_executions multi_cnt, vp.max_tempseg_size max_tmp, vp.last_tempseg_size last_tmp from V$SQL_PLAN_STATISTICS_ALL vp, v$sql where vp.SQL_ID = '8gzkcsvw362s3' and vp.child_number=2 and vp.SQL_ID = v$sql.SQL_ID and v$sql.child_number=2) order by id
16 How do I tune?  Prepare the sql to be run for performance analysis. my_sql.sql Set linesize 300; set pagesize 1000; --Declare variable and assign values var order_id number; execute :order_id:=53759119 SELECT oeh.header_id, oel.line_id FROM oe_order_headers_all oeh, oe_order_lines_all oel WHERE oeh.header_id = :order_id AND oeh.header_id = oel.header_id / select * from table (dbms_xplan.DISPLAY_CURSOR(null, null, 'ALLSTATS')) /
17 Do’s & Don’ts  Do’s 1. Current execution plan and runtime statistics are the first step. 2. Execute a test case first to reproduce.  Don’t 1. Try to use same bind type as application uses. - Literal vs bind variables - number vs varchar2 data type etc 2. Try to use format same as the application for your test case. - CTAS vs INSERT
PLAN_TABLE_OUTPUT SQL_ID cttafpfjwqjdm, child number 0 ------------------------------------- select oeh.header_id,oel.line_id from oe_order_headers_all oeh,oe_order_lines_all oel where oeh.header_id=:order_id and oeh.header_id=oel.header_id Plan hash value: 4180984038 ------------------------------------------------------------------------------------------------------------------------- -- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop | ------------------------------------------------------------------------------------------------------------------------- -- | 0 | SELECT STATEMENT | | | | 11 (100)| | | | | 1 | NESTED LOOPS | | 6 | 114 | 11 (0)| 00:00:01 | | | | 2 | PARTITION HASH SINGLE | | 1 | 6 | 2 (0)| 00:00:01 | KEY | KEY | |* 3 | INDEX UNIQUE SCAN | OE_ORDER_HEADERS_U1 | 1 | 6 | 2 (0)| 00:00:01 | KEY | KEY | | 4 | TABLE ACCESS BY GLOBAL INDEX ROWID| OE_ORDER_LINES_ALL | 6 | 78 | 9 (0)| 00:00:01 | ROWID | ROWID | |* 5 | INDEX RANGE SCAN | OE_ORDER_LINES_N1 | 6 | | 3 (0)| 00:00:01 | | | ------------------------------------------------------------------------------------------------------------------------- -- 18 dbms_xplan.display_cursor
... Predicate Information (identified by operation id): --------------------------------------------------- 3 - access("OEH"."HEADER_ID"=:ORDER_ID) 5 - access("OEL"."HEADER_ID"=:ORDER_ID) Note ----- - Warning These are only collected when: * hint 'gather_plan_statistics' is used for the statement or * parameter 'statistics_level' is set to 'ALL', at session or system level * Cardinality feedback used * Dynamic sampling used 19 dbms_xplan.display_cursor ..2
------------------------------------------------------------------------------------------------------------------------ -- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop | ------------------------------------------------------------------------------------------------------------------------ --- | 0 | SELECT STATEMENT | | | | 11200 (100)| | | | | 1 | NESTED LOOPS | | 6 | 114 | 11 (0)| 00:10:01 | | | | 2 | PARTITION HASH SINGLE | | 1 | 6 | 2 (0)| 00:00:01 | KEY | KEY | |* 3 | INDEX UNIQUE SCAN | OE_ORDER_HEADERS_U1 | 1 | 6 | 2 (0)| 00:00:01 | KEY | KEY | |* 4 | TABLE ACCESS BY GLOBAL INDEX ROWID| OE_ORDER_LINES_ALL | 6 | 78 | 9000 (0)| 00:07:01 | ROWID | ROWID | |* 5 | INDEX RANGE SCAN | OE_ORDER_LINES_N1 | 60000 | | 300 (0)| 00:03:01 | | | ------------------------------------------------------------------------------------------------------------------------ --- Predicate Information (identified by operation id): --------------------------------------------------- 3 - access("OEH"."HEADER_ID"=:ORDER_ID) 4 – filter ("OEL".“OPEN_FLAG=’Y’) 5 - access("OEL"."HEADER_ID"=:ORDER_ID) 20 dbms_xplan: access and filter predicates Added a predicate oel.open_flag=‘Y’
21 Detailed execution statistics  v$sql_plan_statistics_all collects row source level execution statistics  ROWS  CPU  Physical IO  Logical IO  Elapsed time Setting statistics_level=‘ALL’ at system level can be resource intensive and should preferably not be enabled in busy PRODUCTION SYSTEM  To enable at session level set statistics_level=‘ALL’  To enable for all sessions set at system level statistics_level=‘ALL’  To set a SQL statement level add the hint  /*+ gather_plan_statistics */ in the statement.
22 dbms_xplan: script  Modify the script to enable extended execution statistics --my_sql.sql script_name set linesize 300; set pagesize 1000; --Declare variable and assign values var order_id number; execute order_id:=53759119 alter session set statistics_level=‘ALL’; --OR ADD HINT SELECT /*+ gather_plan_statistics */ oeh.header_id, oel.line_id FROM oe_order_headers_all oeh, oe_order_lines_all oel WHERE oeh.header_id = :order_id AND oeh.header_id = oel.header_id /
23 Execution statistics select * from table (dbms_xplan.DISPLAY_CURSOR(null, null, 'ALLSTATS LAST')) / SQL_ID 7gftgf917tg2x, child number 0 ------------------------------------- select /*+ gather_plan_statistics */ oeh.header_id,oel.line_id from oe_order_headers_all oeh,oe_order_lines_all oel where oeh.header_id=:order_id and oeh.header_id=oel.header_id Plan hash value: 4180984038 ------------------------------------------------------------------------------------------------------------------------------ | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | Reads | ------------------------------------------------------------------------------------------------------------------------------ | 0 | SELECT STATEMENT | | 1 | | 4 |00:00:00.03 | 12 | 11 | | 1 | NESTED LOOPS | | 1 | 6 | 4 |00:00:00.03 | 12 | 11 | | 2 | PARTITION HASH SINGLE | | 1 | 1 | 1 |00:00:00.01 | 3 | 3 | |* 3 | INDEX UNIQUE SCAN | OE_ORDER_HEADERS_U1 | 1 | 1 | 1 |00:00:00.01 | 3 | 3 | | 4 | TABLE ACCESS BY GLOBAL INDEX ROWID| OE_ORDER_LINES_ALL | 1 | 6 | 4 |00:00:00.02 | 9 | 8 | |* 5 | INDEX RANGE SCAN | OE_ORDER_LINES_N1 | 1 | 6 | 4 |00:00:00.01 | 5 | 4 | ------------------------------------------------------------------------------------------------------------------------------ Predicate Information (identified by operation id): --------------------------------------------------- 3 - access("OEH"."HEADER_ID"=:ORDER_ID) 5 - access("OEL"."HEADER_ID"=:ORDER_ID) 25 rows selected.
24 Alias select * from table (dbms_xplan.DISPLAY_CURSOR(null, null, 'ALLSTATS LAST +alias -predicate')); SELECT /*+ gather_plan_statistics */ oel.line_id FROM oe_order_lines_all oel WHERE oel.open_flag = 'Y' and exists (select 1 from oe_order_headers_all oeh where oeh.header_id = oel.header_id and oeh.open_flag='Y' and oeh.last_update_date > sysdate -5) Plan hash value: 746840967 -------------------------------------------------------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | OMem | 1Mem | Used-Mem | -------------------------------------------------------------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 3 |00:00:00.01 | 16 | | | | | 1 | NESTED LOOPS | | 1 | | 3 |00:00:00.01 | 16 | | | | | 2 | NESTED LOOPS | | 1 | 1 | 3 |00:00:00.01 | 10 | | | | | 3 | SORT UNIQUE | | 1 | 1 | 1 |00:00:00.01 | 5 | 2048 | 2048 | 2048 (0)| | 4 | TABLE ACCESS BY GLOBAL INDEX ROWID| OE_ORDER_HEADERS_ALL | 1 | 1 | 1 |00:00:00.01 | 5 | | | | | 5 | INDEX RANGE SCAN | CCW_OE_ORD_HEADERS_ALL_D1 | 1 | 7 | 1 |00:00:00.01 | 4 | | | | | 6 | INDEX RANGE SCAN | OE_ORDER_LINES_N1 | 1 | 6 | 3 |00:00:00.01 | 5 | | | | | 7 | TABLE ACCESS BY GLOBAL INDEX ROWID | OE_ORDER_LINES_ALL | 3 | 1 | 3 |00:00:00.01 | 6 | | | | -------------------------------------------------------------------------------------------------------------------------------------------------------- Query Block Name / Object Alias (identified by operation id): ------------------------------------------------------------- 1 - SEL$5DA710D3 4 - SEL$5DA710D3 / OEH@SEL$2 5 - SEL$5DA710D3 / OEH@SEL$2 6 - SEL$5DA710D3 / OEL@SEL$1 7 - SEL$5DA710D3 / OEL@SEL$1
SQL_ID cu2f3xhzy75vc, child number 0 ------------------------------------- SELECT /*+ gather_plan_statistics qb_name(outer_block) */ oel.line_id FROM oe_order_lines_all oel WHERE oel.open_flag = 'Y' and exists (select /*+ qb_name(innner_block) */ 1 from oe_order_headers_all oeh where oeh.header_id = oel.header_id and oeh.open_flag='Y' and oeh.last_update_date > sysdate -5); Plan hash value: 746840967 -------------------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | ..| --------------------------------------------------------------------------------------------------------------------.. | 0 | SELECT STATEMENT | | 1 | | 3 |00:00:00.01 | … Query Block Name / Object Alias (identified by operation id): ------------------------------------------------------------- 1 - SEL$8E94A21F 4 - SEL$8E94A21F / OEH@INNNER_BLOCK 5 - SEL$8E94A21F / OEH@INNNER_BLOCK 6 - SEL$8E94A21F / OEL@OUTER_BLOCK 7 - SEL$8E94A21F / OEL@OUTER_BLOCK 25 Query Block name
26 Default QB Name Prefix Row Source operation CRI$ Create index statement DEL$ DELETE statement INS$ Insert Statement MISC$ Miesc SQL like lock table MRG$ Merge Statement SEL$ SELECT statement SET$ Set operators UPD$ Update statement
27 Hints or Outlines set linesize 300 set pagesize 300 alter session set statistics_level='ALL'; SELECT /* outline query */ RECID, ALC, FRC ... FROM ORD_AP_IF_TASK WHERE PROCESSED_FLAG = 'U') ORDER BY TABLENAME, CREATION_DATE; select * from table( dbms_xplan.display_cursor (null,null,'ALLSTATS LAST +outline')) /
Outline Data ------------- /*+ BEGIN_OUTLINE_DATA IGNORE_OPTIM_EMBEDDED_HINTS OPTIMIZER_FEATURES_ENABLE('11.2.0.2') OPT_PARAM('_b_tree_bitmap_plans' 'false') OPT_PARAM('_fast_full_scan_enabled' 'false') ALL_ROWS OUTLINE_LEAF(@"SEL$2") OUTLINE_LEAF(@"SEL$1") FULL(@"SEL$3" "ORD_AP_IF_TASKS"@"SEL$3") INDEX_RS_ASC(@"SEL$2" "ORD_AP_IF_PROJECTS"@"SEL$2“ ("ORD_AP_IF_PROJECTS"."PROCESSED_FLAG")) END_OUTLINE_DATA */ 28 Outline --------------------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | … -------------------------------------------------------------------------------------------------------------------… | 0 | SELECT STATEMENT | | 1 | | 0 |00:00:27.40 | 153K| .. | 1 | SORT ORDER BY | | 1 | 2146K| 0 |00:00:27.40 | 153K| … | 2 | VIEW | | 1 | 2146K| 0 |00:00:27.40 | 153K| … | 3 | SORT UNIQUE | | 1 | 2146K| 0 |00:00:27.40 | 153K| … | 4 | UNION-ALL | | 1 | | 0 |00:00:27.40 | 153K| … | 5 | TABLE ACCESS BY INDEX ROWID| ORD_AP_IF_PROJECTS | 1 | 1 | 0 |00:00:00.01 | 3 | … | 6 | INDEX RANGE SCAN | ORD_AP_IF_PROJECTS_N1 | 1 | 1 | 0 |00:00:00.01 | 3 | | 7 | TABLE ACCESS FULL | ORD_AP_IF_TASKS | 1 | 2146K| 0 |00:00:27.40 | 153K| -------------------------------------------------------------------------------------------------------------------
Outline Data ------------- /*+ Predicate Information (identified by operation id): --------------------------------------------------- 6 - access("PROCESSED_FLAG"='U') 7 - filter("PROCESSED_FLAG"='U') ... FULL(@"SEL$3" "ORD_AP_IF_TASKS"@"SEL$3") INDEX_RS_ASC(@"SEL$2" "ORD_AP_IF_PROJECTS "@"SEL$2" ("ORD_AP_IF_PROJECTS"."PROCESSED_FLAG")) END_OUTLINE_DATA */ 29 Tuning SQL SQLPLUS> select count(1) from ORD_AP_IF_TASKS where PROCESSED_FLAG='U'; COUNT(1) ---------- 0 There is an index on ORD_AP_IF_TASKS.PROCESSED_FLAG
set linesize 300 set pagesize 300 alter session set statistics_level='ALL'; SELECT /*+ Copying outline as hint; Altering Full Table Scan to Index Range Scan. BEGIN_OUTLINE_DATA IGNORE_OPTIM_EMBEDDED_HINTS OPTIMIZER_FEATURES_ENABLE('11.2.0.2') DB_VERSION('11.2.0.2') OPT_PARAM('_b_tree_bitmap_plans' 'false') OPT_PARAM('_fast_full_scan_enabled' 'false') ALL_ROWS OUTLINE_LEAF(@"SEL$2") OUTLINE_LEAF(@"SEL$3") OUTLINE_LEAF(@"SET$1") OUTLINE_LEAF(@"SEL$1") NO_ACCESS(@"SEL$1" "from$_subquery$_001"@"SEL$1") INDEX_RS_ASC(@"SEL$3" “ORD_AP_IF_TASKS"@"SEL$3" (“ORD_AP_IF_TASKS"."PROCESSED_FLAG")) INDEX_RS_ASC(@"SEL$2" “ORD_AP_IF_PROJECTS"@"SEL$2" (“ORD_AP_IF_PROJECTS"."PROCESSED_FLAG")) END_OUTLINE_DATA */ WHERE PROCESSED_FLAG = 'U') ORDER BY TABLENAME, CREATION_DATE / select * from table(dbms_xplan.display_cursor (null,null,'ALLSTATS LAST +outline')) / 30 Bob the Builder FULL(@"SEL$3" "ORD_AP_IF_TASKS"@"SEL$3")
Tuned Plan ---------------------------------------------------------------------------------------------------------… | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | --------------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 0 |00:00:00.01 | | 1 | SORT ORDER BY | | 1 | 2146K| 0 |00:00:00.01 | | 2 | VIEW | | 1 | 2146K| 0 |00:00:00.01 | | 3 | SORT UNIQUE | | 1 | 2146K| 0 |00:00:00.01 | | 4 | UNION-ALL | | 1 | | 0 |00:00:00.01 | | 5 | TABLE ACCESS BY INDEX ROWID| ORD_AP_IF_PROJECTS | 1 | 1 | 0 |00:00:00.01 | |* 6 | INDEX RANGE SCAN | ORD_AP_IF_PROJECTS_N1 | 1 | 1 | 0 |00:00:00.01 | | 7 | TABLE ACCESS BY INDEX ROWID| ORD_AP_IF_TASKS | 1 | 2146K| 0 |00:00:00.01 | |* 8 | INDEX RANGE SCAN | ORD_AP_IF_TASKS_N1 | 1 | 2173K| 0 |00:00:00.01 | ---------------------------------------------------------------------------------------------------------… Outline Data ------------- 31 /*+ BEGIN_OUTLINE_DATA IGNORE_OPTIM_EMBEDDED_HINTS OPT_PARAM('_b_tree_bitmap_plans' 'false') OPT_PARAM('_fast_full_scan_enabled' 'false') ALL_ROWS OUTLINE_LEAF(@"SEL$1") NO_ACCESS(@"SEL$1" "from$_subquery$_001"@"SEL$1") INDEX_RS_ASC(@"SEL$3" “ORD_AP_IF_TASKS"@"SEL$3" (“ORD_A__IF_TASKS"."PROCESSED_FLAG")) INDEX_RS_ASC(@"SEL$2" “ORD_AP_IF_PROJECTS"@"SEL$2" (“ORD_AP_IF_PROJECTS"."PROCESSED_FLAG")) END_OUTLINE_DATA */ Predicate Information (identified by operation id): --------------------------------------------------- 6 - access("PROCESSED_FLAG"='U') 8 - access("PROCESSED_FLAG"='U’)
So many details..So little space.. Column Description Always available columns id Identified of each step in the execution plan; if prefixed with * then predicate information available in predicate section Operation Row source operation Name The database object in the operation CBO parse time information Rows Estimated number of rows returned by the row source operation; derived from statistics on names object in the operation Bytes Estimated amount of data returned by the operation TempSpc The estimated amount of temp space usage by the operation Cost(%CPU) The estimated cost of the row source operation. The percentage CPU cost is given in () for individual row source operation Time Estimated amount of time needed to execute that operation in HH:MM:SS Partitioning Pstart Number of first partition to be accessed Pstop The number of last partition to be accessed Parallel Processing TQ Table queue used for processing IN-OUT The relation between parallel operations PQ Distrib The distribution used by producers to send data to consumers Runtime Statistics Starts The number of times operation was executed (check more nested loop joins operation) A-Rows Actual number of rows returned A-Time Actual amount of time spent executing the operation I/O Statistics Buffers Logical reads operations performed during execution of each step Read Physical reads performed for each operation Write Physical writes performed 32
33 dbms_xplan.display_awr  Displays plans stored in AWR; Format select * from table(dbms_xplan.display_awr(‘sql_id’,plan_hash_value,db_id,’format’)); -plan_hash_value: to select a specific plan -dbid : specifies which database to select from Example script: SELECT * FROM TABLE( dbms_xplan.display_awr('&&sql_id', '&plan_hash_value', NULL, 'ALL +peeked_binds') );
34 dbms_xplan.display_awr select * from table(dbms_xplan.display_awr('4jtbgawt37mcd',null, null, 'ALL +peeked_binds')); SQL_ID 4jtbgawt37mcd -------------------- Plan hash value: 327243540 --------------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | --------------------------------------------------------------------------------------------------------------- Peeked Binds (identified by position): -------------------------------------- 1 - :B3 (NUMBER): 7394 2 - :B2 (VARCHAR2(30), CSID=871): 'AAL' 3 - :B1 (VARCHAR2(30), CSID=871): '73057' SQL_ID 4jtbgawt37mcd -------------------- Plan hash value: 2294473928 --------------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | --------------------------------------------------------------------------------------------------------------- Peeked Binds (identified by position): -------------------------------------- 1 - :B3 (NUMBER): 9649 2 - :B2 (VARCHAR2(30), CSID=871): 'ZXU' 3 - :B1 (VARCHAR2(30), CSID=871): 'U5152'
Cardinality feedback select /*+ gather_plan_statistics */ max(length(v1)) from order_headers_all where processed_flag='N' --------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | --------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 1 | | 1 | SORT AGGREGATE | | 1 | 1 | 1 | |* 2 | TABLE ACCESS FULL| ORDER_HEADERS_ALL | 1 | 50000 | 10 | --------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - filter("PROCESSED_FLAG"='N') ©OraInternals Riyaj Shamsudeen 35 Plan hash value: 872302569 Demo @demo_oh1.sql
/*+ no_rewrite gather_plan_statistics */ MAX(LENGTH(oh.v1)), MAX(LENGTH(oh.v1)) FROM order_headers_all oh WHERE EXISTS ( SELECT 1 FROM order_lines_all ol WHERE oh.order_id = ol.order_id AND line_processed_flag = 'Y' AND rownum >=1 AND oh.processed_flag='N' ; ©OraInternals Riyaj Shamsudeen 36 Starts SELECT ) Demo @demo_oh2.sql How many times did the EXISTS Subquery was executed?
ALLSTATS LAST select * from table (dbms_xplan.display_cursor ('', '','ALLSTATS LAST')) ---------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | ---------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 1 | | 1 | SORT AGGREGATE | | 1 | 1 | 1 | |* 2 | FILTER | | 1 | | 10 | |* 3 | TABLE ACCESS FULL | ORDER_HEADERS_ALL | 1 | 50000 | 10 | | 4 | COUNT | | 10 | | 10 | |* 5 | FILTER | | 10 | | 10 | |* 6 | TABLE ACCESS BY INDEX ROWID| ORDER_LINES_ALL | 10 | 1 | 10 | |* 7 | INDEX RANGE SCAN | OL_N1 | 10 | 1 | 10 | ---------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - filter( IS NOT NULL) 3 - filter("OH"."PROCESSED_FLAG"='N') 5 - filter(ROWNUM>=1) 6 - filter("LINE_PROCESSED_FLAG"='Y') 7 - access("OL"."ORDER_ID"=:B1) ©OraInternals Riyaj Shamsudeen 37 Demo @demo_oh2.sql
Starts ..2 select * from table (dbms_xplan.display_cursor ('', '','ALLSTATS')) SELECT 1 FROM PA_TASKS WHERE TASK_ID = :B1 ©OraInternals Riyaj Shamsudeen 38 Plan hash value: 357090087 -------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | -------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 256K| | 246K| |* 1 | INDEX UNIQUE SCAN| PA_TASKS_U1 | 256K| 1 | 246K| -------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 1 - access("TASK_ID"=:B1) How many times did we execute this statement?
Cardinality feedback ..2 select * from table (dbms_xplan.display_cursor ('', '','ALLSTATS')) ------------------------------------------------------------------------------------------ | Id | Operation | Name | Starts | E-Rows | A-Rows | ------------------------------------------------------------------------------------------ | 0 | UPDATE STATEMENT | | 7822 | | 0 | | 1 | UPDATE | ENI_OLTP_ITEM_STAR | 7822 | | 0 | |* 2 | FILTER | | 7824 | | 7254K| |* 3 | TABLE ACCESS BY ROWID RANGE| ENI_OLTP_ITEM_STAR | 7823 | 69121 | 7256K| | 4 | TABLE ACCESS BY INDEX ROWID | MTL_SYSTEM_ITEMS_B | 7171K| 1 | 7167K| |* 5 | INDEX UNIQUE SCAN | MTL_SYSTEM_ITEMS_B_U1 | 7176K| 1 | 7172K| ------------------------------------------------------------------------------------------ ©OraInternals Riyaj Shamsudeen 39
Cardinality feedback ..3 select * from table (dbms_xplan.display_cursor ('', '','ALLSTATS')) ------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | A-Time | Buffers | Reads | ------------------------------------------------------------------------------------------------------- | 0 | UPDATE STATEMENT | | 7822 |00:47:24.86 | 56M| 1082K| | 1 | UPDATE | ENI_OLTP_ITEM_STAR | 7822 |00:47:24.86 | 56M| 1082K| |* 2 | FILTER | | 7824 |00:01:27.46 | 23M| 868 | |* 3 | TABLE ACCESS BY ROWID RANGE| ENI_OLTP_ITEM_STAR | 7823 |00:01:23.30 | 23M| 868 | | 4 | TABLE ACCESS BY INDEX ROWID | MTL_SYSTEM_ITEMS_B | 7171K|00:41:09.13 | 25M| 1028K| |* 5 | INDEX UNIQUE SCAN | MTL_SYSTEM_ITEMS_B_U1 | 7176K|00:01:17.74 | 17M| 488 | ------------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - filter(CHARTOROWID(:B2)<=CHARTOROWID(:B1)) 3 - access(ROWID>=CHARTOROWID(:B2) AND ROWID<=CHARTOROWID(:B1)) 5 - access("MTI"."INVENTORY_ITEM_ID"=:B1 AND "MTI"."ORGANIZATION_ID"=:B2) ©OraInternals Riyaj Shamsudeen 40
SQL - remote (SELECT /*+ materialize */ order_id FROM oli_table@orcl2 ol WHERE line_processed_flag='Y' ) SELECT /*+ no_rewrite gather_plan_statistics */ MAX(LENGTH(oh.v1)) FROM order_headers_all oh (SELECT 1 FROM rem1 WHERE oh.order_id = rem1.order_id ) AND oh.processed_flag='N' ; ©OraInternals Riyaj Shamsudeen 41 WITH rem1 AS WHERE EXISTS Demo @demo_oh3.sql
Remote queries --------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | --------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 1 | | 1 | TEMP TABLE TRANSFORMATION | | 1 | | 1 | | 2 | LOAD AS SELECT | | 1 | | 0 | | 3 | REMOTE | OLI_TABLE | 1 | 100K| 100K| | 4 | SORT AGGREGATE | | 1 | 1 | 1 | |* 5 | HASH JOIN RIGHT SEMI | | 1 | 50000 | 10 | | 6 | VIEW | | 1 | 100K| 100K| | 7 | TABLE ACCESS FULL | SYS_TEMP_0FD9FC884_E8A367F2 | 1 | 100K| 100K| |* 8 | TABLE ACCESS FULL | ORDER_HEADERS_ALL | 1 | 50000 | 10 | --------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 5 - access("OH"."ORDER_ID"="REM1"."ORDER_ID") 8 - filter("OH"."PROCESSED_FLAG"='N') … Remote SQL Information (identified by operation id): ---------------------------------------------------- 3 - SELECT /*+ */ "ORDER_ID","LINE_PROCESSED_FLAG" FROM "OLI_TABLE" "OL" WHERE LINE_PROCESSED_FLAG"='Y' (accessing ©OraInternals Riyaj Shamsudeen 42 ‘ORCL2.ORACLE.com' ) Demo @demo_oh3.sql ADVANCED option provides remote query output
SQL – remote ..2 /*+ no_rewrite gather_plan_statistics use_nl (oh ol) */ MAX(LENGTH(oh.v1)) FROM order_headers_all oh, (SELECT order_id FROM oli_table@orcl2 ol WHERE line_processed_flag='Y' ) ol WHERE oh.order_id = ol.order_id AND oh.processed_flag='N' ; ©OraInternals Riyaj Shamsudeen 43 SELECT Demo @demo_oh3.sql
Remote queries (2) ------------------------------------------------------------------------------------ | Id | Operation | Name | Rows | Bytes | Cost (%CPU)|IN-OUT| ------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | | | 100K(100)| | | 1 | SORT AGGREGATE | | 1 | 223 | | | | 2 | NESTED LOOPS | | 50000 | 10M| 100K (1)| | |* 3 | TABLE ACCESS FULL| ORDER_HEADERS_ALL | 50000 | 9M| 403 (7)| | | 4 | REMOTE | OLI_TABLE | 1 | 15 | 2 (0)| R->S | ------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 3 - filter("OH"."PROCESSED_FLAG"='N') Remote SQL Information (identified by operation id): ---------------------------------------------------- 4 - SELECT /*+ USE_NL ("OL") */ "ORDER_ID", "LINE_PROCESSED_FLAG" FROM "OLI_TABLE" "OL" WHERE "LINE_PROCESSED_FLAG"='Y' AND :1="ORDER_ID“ (accessing ‘ORCL2.ORCL.COM' ) ©OraInternals Riyaj Shamsudeen 44 Demo @demo_oh5.sql
Parallel Queries ---------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | ---------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 1 |00:00:08.83 | | 1 | SORT AGGREGATE | | 1 | 1 | 1 |00:00:08.83 | |* 2 | HASH JOIN | | 1 | 999K| 260K|00:00:08.76 | | 3 | VIEW | | 1 | 999K| 999K|00:00:02.11 | |* 4 | COUNT STOPKEY | | 1 | | 999K|00:00:01.52 | | 5 | PX COORDINATOR | | 1 | | 999K|00:00:00.84 | | 6 | PX SEND QC (RANDOM) | :TQ10000 | 0 | 11M| 0 |00:00:00.01 | |* 7 | COUNT STOPKEY | | 0 | | 0 |00:00:00.01 | | 8 | PX PARTITION HASH ALL| | 0 | 11M| 0 |00:00:00.01 | | 9 | INDEX FULL SCAN | OE_ORDER_HEADERS_U1 | 0 | 11M| 0 |00:00:00.01 | | 10 | VIEW | | 1 | 999K| 999K|00:00:02.28 | |* 11 | COUNT STOPKEY | | 1 | | 999K|00:00:01.68 | | 12 | INDEX FULL SCAN | OE_ORDER_LINES_N1 | 1 | 57M| 999K|00:00:00.98 | ---------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - access("OH"."HEADER_ID"="OL"."HEADER_ID") 4 - filter(ROWNUM<1000000) 7 - filter(ROWNUM<1000000) 11 - filter(ROWNUM<1000000) ©OraInternals Riyaj Shamsudeen 45 Note ----- - Degree of Parallelism is 8 because of hint ALLSTATS LAST Also, notice the broken cardinality Feedback.
Parallel Queries After 1 execution with DOP=8 --------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | ---------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 1 |00:00:08.83 | | 1 | SORT AGGREGATE | | 1 | 1 | 1 |00:00:08.83 | |* 2 | HASH JOIN | | 1 | 999K| 260K|00:00:08.76 | | 3 | VIEW | | 1 | 999K| 999K|00:00:02.11 | |* 4 | COUNT STOPKEY | | 1 | | 999K|00:00:01.52 | | 5 | PX COORDINATOR | | 1 | | 999K|00:00:00.84 | | 6 | PX SEND QC (RANDOM) | :TQ10000 | 0 | 11M| 0 |00:00:00.01 | |* 7 | COUNT STOPKEY | | 8 | | 1072K|00:00:03.83 | | 8 | PX PARTITION HASH ALL| | 8 | 11M| 1072K|00:00:03.17 | | 9 | INDEX FULL SCAN | OE_ORDER_HEADERS_U1 | 8 | 11M| 1072K|00:00:02.56 | | 10 | VIEW | | 1 | 999K| 999K|00:00:02.28 | |* 11 | COUNT STOPKEY | | 1 | | 999K|00:00:01.68 | | 12 | INDEX FULL SCAN | OE_ORDER_LINES_N1 | 1 | 57M| 999K|00:00:00.98 | ---------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - access("OH"."HEADER_ID"="OL"."HEADER_ID") 4 - filter(ROWNUM<1000000) 7 - filter(ROWNUM<1000000) 11 - filter(ROWNUM<1000000) ©OraInternals Riyaj Shamsudeen 46 Note ----- - Degree of Parallelism is 8 because of hint ALLSTATS
Parallel Queries After 4 executions with DOP=16 ---------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | ---------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 4 | | 4 |00:00:38.25 | | 1 | SORT AGGREGATE | | 4 | 1 | 4 |00:00:38.25 | |* 2 | HASH JOIN | | 4 | 999K| 418K|00:00:38.16 | | 3 | VIEW | | 4 | 999K| 3999K|00:00:07.67 | |* 4 | COUNT STOPKEY | | 4 | | 3999K|00:00:05.53 | | 5 | PX COORDINATOR | | 4 | | 3999K|00:00:03.12 | | 6 | PX SEND QC (RANDOM) | :TQ10000 | 0 | 11M| 0 |00:00:00.01 | |* 7 | COUNT STOPKEY | | 64 | | 4779K|00:00:56.27 | | 8 | PX PARTITION HASH ALL| | 64 | 11M| 4779K|00:00:53.19 | | 9 | INDEX FULL SCAN | OE_ORDER_HEADERS_U1 | 64 | 11M| 4779K|00:00:50.33 | | 10 | VIEW | | 4 | 999K| 3999K|00:00:14.59 | |* 11 | COUNT STOPKEY | | 4 | | 3999K|00:00:12.32 | | 12 | PX COORDINATOR | | 4 | | 3999K|00:00:09.35 | | 13 | PX SEND QC (RANDOM) | :TQ20000 | 0 | 57M| 0 |00:00:00.01 | |* 14 | COUNT STOPKEY | | 64 | | 4169K|00:05:45.40 | | 15 | PX BLOCK ITERATOR | | 64 | 57M| 4169K|00:05:42.68 | |* 16 | TABLE ACCESS FULL | OE_ORDER_LINES_ALL | 233 | 57M| 4169K|00:05:26.98 | ---------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- .. ©OraInternals Riyaj Shamsudeen 47 Note ----- - Degree of Parallelism is 16 because of hint ALLSTATS
©OraInternals Riyaj Shamsudeen 48 Note section Note ----- - dynamic sampling used for this statement (level=2) Note ----- - SQL profile “SQL_PROF_4awcsbtwr8ksz" used for this statement Note ----- - Cardinality feedback used
Few limitations  Display_awr does not store predicates.  Of course , not all SQL statements are stored in AWR repository (color important statements).  Display_cursor is not RAC aware. You can query the plans only from the local instances using display_cursor.  Run time statistics are printed only after the completion of SQL statements (Think production long running queries). ©OraInternals Riyaj Shamsudeen 49
©OraInternals Riyaj Shamsudeen 50 SQL monitor SET LONG 1000000 SET LONGCHUNKSIZE 1000000 SET LINESIZE 1000 SET PAGESIZE 0 SET TRIM ON SET TRIMSPOOL ON SET ECHO OFF SET FEEDBACK OFF SELECT DBMS_SQLTUNE.report_sql_monitor( sql_id => '&sql_id', type=>'TEXT' , report_level => 'ALL') from dual /
©OraInternals Riyaj Shamsudeen 51 Output
Output ..2 ©OraInternals Riyaj Shamsudeen 52
53 A Presentation sponsored by
©OraInternals Riyaj Shamsudeen 54 Riyaj Shamsudeen  19 years using Oracle products/DBA  OakTable member  Oracle ACE Director  Certified DBA versions 7.0,7.3,8,8i,9i &10g  Specializes in RAC, performance tuning, Internals and E-business suite  Chief DBA with OraInternals  Co-author few books  Email: rshamsud@orainternals.com  Blog : orainternals.wordpress.com  Web: www.orainternals.com
Thank you for attending! If you like this presentation, you will love my 2-part intensive, online RAC webinar. http://www.orainternals.com/training/advanced-rac-training Email: rshamsud@gmail.com Week Dates Time Week1 TBA 8AM – 2PM PDT Week 2 TBA 8AM - 2PM PDT ©OraInternals Riyaj Shamsudeen 55
©OraInternals Riyaj Shamsudeen 56 References • Oracle support site. Metalink.oracle.com. Various documents • Troubleshooting Oracle performance - Christian Antongini • http://www.orainternals.com/papers - Riyaj Shamsudeen • Various article from web led through on google search • Tom Kyte’s website Asktom.oracle.com

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Dbms plan - A swiss army knife for performance engineers

  • 1.
    dbms_xplan: A Swissarmy knife for performance engineers Sahil Thapar Riyaj Shamsudeen
  • 2.
    2 Disclaimer Theseslides and materials represent the work and opinions of the author and do not constitute official positions of my current or past employer or any other organization. This material has been peer reviewed, but author assume no responsibility whatsoever for the test cases. If you corrupt your databases by running my scripts, you are solely responsible for that.
  • 3.
    3 Options EXPLAINPLAN (Version 7 or older) AUTOTRACE ( Version 8i +) SQL_TRACE (Version 7) DBMS_XPLAN Estimated, not always reliable Actual plan, buggy. Actual plan; but must enable trace before the run. Actual plan, after the run, always available.
  • 4.
    PARSING IN CURSOR#1844674 len=1000 dep=0 uid=173 oct=3 lid=173 tim=7861072491388 hv=2701626457 ad='498d8f1d0' sqlid='9sup9gfhhg32t' SELECT RECID, TABLENAME, PROJECT_NUMBER, PROJECT_NAME, CARRYING_OUT_ORGANIZATION, ...FROM ( SELECT STGTBL_RECID ... WHERE PROCESSED_FLAG='U' ) ORDER BY TABLENAME, CREATION_DATE PARSE:#1844674:c=10000,e=10162,p=0,cr=0,cu=0,mis=1,r=0,dep=0,og=1,plh=3298327531,tim=78610 72491386 EXEC:#1844674:c=0,e=139,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=3298327531,tim=786107249172 3 EXEC:#1844674:c=0,e=139,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=3298327531,tim=786107249172 3 .. WAIT #1844674: nam='Disk file operations I/O' ela= 2013 FileOperation=2 fileno=811 filetype=2 obj#=706379 tim=786107 FETCH#1844674:c=18020000,e=59603730,p=199262,cr=199331,cu=0,mis=0,r=0,dep=0,og=1,plh=32983 27531,tim=7861 … STAT #1844674 id=3 cnt=0 pid=2 pos=1 obj=0 op='SORT UNIQUE (cr=199331 pr=199262 pw=0 time=59603707 us cost=56817 size=126622640 card=2146146)' STAT #1844674 id=4 cnt=0 pid=3 pos=1 obj=0 op='UNION-ALL (cr=199331 pr=199262 pw=0 time=59603638 us)' 4 Raw trace file Content of a sql trace file:
  • 5.
    5 tkprof (1) SELECT RECID, TABLENAME, PROJECT_NUMBER, PROJECT_NAME, CARRYING_OUT_ORGANIZATION, COMPANY, CHARGEABLE_FLAG, START_DATE, END_DATE, CREATION_DATE, LAST_UPDATE_DATE, PROCESSED_FLAG, ………………………………. …………………………….. WHERE PROCESSED_FLAG='U' ) ORDER BY TABLENAME, CREATION_DATE call count cpu elapsed disk query current rows ------- ------ -------- ---------- ---------- ---------- ---------- ---------- Parse 1 0.01 0.01 0 0 0 0 Execute 1 0.00 0.00 0 0 0 0 Fetch 1 18.02 59.60 199262 199331 0 0 ------- ------ -------- ---------- ---------- ---------- ---------- ---------- total 3 18.03 59.61 199262 199331 0 0
  • 6.
    6 tkprof (2) Rows (max) Row Source Operation ---------- --------------------------------------------------- 0 SORT ORDER BY (cr=199331 pr=199262 pw=0 time=59603767 us cost=180933 size=641697654 card=2146146) 0 VIEW (cr=199331 pr=199262 pw=0 time=59603722 us cost=56817 size=641697654 card=2146146) 0 SORT UNIQUE (cr=199331 pr=199262 pw=0 time=59603707 us cost=56817 size=126622640 card=2146146) 0 UNION-ALL (cr=199331 pr=199262 pw=0 time=59603638 us) 0 TABLE ACCESS FULL ORD_AP_IF_PROJECTS (cr=46025 pr=45963 pw=0 time=17088312 us cost=6568 size=85 card=1) 0 TABLE ACCESS FULL ORD_AP_IF_TASKS (cr=153306 pr=153299 pw=0 time=42515291 us cost=21894 size=126622555 Elapsed times include waiting on following events: Event waited on Times Max. Wait Total Waited ---------------------------------------- Waited ---------- ------------ SQL*Net message to client 1 0.00 0.00 Disk file operations I/O 129 0.01 0.26
  • 7.
    7 Usage Displays execution plan stored in three different places 1) PLAN_TABLE dbms_xplan.diplay (estimated plan) 2) SGA of instance dbms_xplan.display_cursor (real plan from memory) 3) AWR dbms_xplan.display_awr (real,history plan from AWR)
  • 8.
    8 Comparison SlTkprof Dbms_xplan 1 Trace must be enabled. Basic statistics are available in memory and AWR 2 CBO notes are not visible Note section is very useful 3 No predicate Predicates printed from memory. 4 Bind values can be retrieved with ease 5 Plan history can be retrieved easily.
  • 9.
    select * fromtable(dbms_xplan.display_cursor(‘sql_id’,child_number,’format’)); 9 dbms_xplan format arguments Format Examples: select * from table( dbms_xplan.display_cursor()); select * from table ( dbms_xplan.display_cursor (null,null, 'ADVANCED')); select * from table ( dbms_xplan.display_cursor ('811a0zb26fw0x',0, 'BASIC')); select * from table ( dbms_xplan.display_cursor ('811a0zb26fw0x',0, ‘ALL -projection')); select * from table ( dbms_xplan.display_cursor ('811a0zb26fw0x',0, ‘ALL +peeked_binds')); Format arguments: ' ADVANCED' ' –PREDICATE' ' –PREDICATE +OUTLINE' TYPICAL is the default class Format arguments combination: Class level alias bytes cost note predicate parallel partition projection outlines peeked_binds remote rows BASIC null X X X X X TYPICAL X X X X X X X X SERIAL X X X X X X ALL X X X X X X X X X X X ADVANCED X X X X X X X X X X X X
  • 10.
    SQL_ID 9sup9gfhhg32t, childnumber 0 ------------------------------------- SELECT RECID, TABLENAME, PROJECT_NUMBER, PROJECT_NAME, ……………………………………………………………………………………………L EDIT_CLASS_CODE, ALC, FRC FROM CCW_PA_IF_TASKS WHERE PROCESSED_FLAG='U' ) ORDER BY TABLENAME, CREATION_DATE Plan hash value: 3298327531 --------------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes |TempSpc| Cost (%CPU)| Time | ---------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | | | | 180K(100)| | | 1 | SORT ORDER BY | | 2146K| 611M| 698M| 180K (5)| 00:09:03 | | 2 | VIEW | | 2146K| 611M| | 56817 (10)| 00:02:51 | | 3 | SORT UNIQUE | | 2146K| 120M| 172M| 56817 (91)| 00:02:51 | | 4 | UNION-ALL | | | | | | | |* 5 | TABLE ACCESS FULL| ORD_AP_IF_PROJECTS | 1 | 85 | | 6568 (14)| 00:00:20 | |* 6 | TABLE ACCESS FULL| ORD_AP_IF_TASKS | 2146K| 120M| | 21894 (14)| 00:01:06 | ---------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 5 - filter("PROCESSED_FLAG"='U') 6 - filter("PROCESSED_FLAG"='U') Note ----- - SQL profile not used for this statement 10 dbms_xplan.display Optimizer estimates
  • 11.
    11 Display_cursor select* from table(dbms_xplan.display_cursor('9yx90c0nwv9tk',0,'allstats')); SQL_ID 9yx90c0nwv9tk, child number 0 ------------------------------------- SELECT /* gather_plan_statistics */ RECID, TABLENAME, ... Plan hash value: 3298327531 --------------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | Reads | --------------------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 0 |00:00:32.50 | 199K| 199K| | 1 | SORT ORDER BY | | 1 | 2146K| 0 |00:00:32.50 | 199K| 199K| | 2 | VIEW | | 1 | 2146K| 0 |00:00:32.50 | 199K| 199K| | 3 | SORT UNIQUE | | 1 | 2146K| 0 |00:00:32.50 | 199K| 199K| | 4 | UNION-ALL | | 1 | | 0 |00:00:32.50 | 199K| 199K| |* 5 | TABLE ACCESS FULL| ORD_AP_IF_PROJECTS | 1 | 1 | 0 |00:00:07.90 | 46025 | 45963 | |* 6 | TABLE ACCESS FULL| ORD_AP_IF_TASKS | 1 | 2146K| 0 |00:00:24.60 | 153K| 153K| --------------------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 5 - filter("PROCESSED_FLAG"='U') 6 - filter("PROCESSED_FLAG"='U') Note, output formatted to fit screen
  • 12.
    12 Easily quantifythe solution given.. select * from table(dbms_xplan.display_cursor('9yx90c0nwv9tk',0,'allstats')); Plan hash value: 932773089 ---------------------------------------------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | OMem | 1Mem | Used-Mem | ---------------------------------------------------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 0 |00:00:00.01 | 6 | | | | | 1 | SORT ORDER BY | | 1 | 2146K| 0 |00:00:00.01 | 6 | 1024 | 1024 | | | 2 | VIEW | | 1 | 2146K| 0 |00:00:00.01 | 6 | | | | | 3 | SORT UNIQUE | | 1 | 2146K| 0 |00:00:00.01 | 6 | 1024 | 1024 | | | 4 | UNION-ALL | | 1 | | 0 |00:00:00.01 | 6 | | | | | 5 | TABLE ACCESS BY INDEX ROWID| ORD_PA_IF_PROJECTS | 1 | 1 | 0 |00:00:00.01 | 3 | | | | |* 6 | INDEX RANGE SCAN | ORD_PA_IF_PROJECTS_N1 | 1 | 1 | 0 |00:00:00.01 | 3 | | | | | 7 | TABLE ACCESS BY INDEX ROWID| ORD_PA_IF_TASKS | 1 | 2146K| 0 |00:00:00.01 | 3 | | | | |* 8 | INDEX RANGE SCAN | ORD_PA_IF_TASKS_N1 | 1 | 2173K| 0 |00:00:00.01 | 3 | | | | ---------------------------------------------------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 6 - access("PROCESSED_FLAG"='U') 8 - access("PROCESSED_FLAG"='U') Note -----
  • 13.
    13 Privileges Privileges needed to execute dbms_xplan For dbms_xplan.display_cursor grant select on v_$session to scott; grant select on v_$SQL_PLAN_STATISTICS_ALL to scott; grant select on v_$sql to scott; grant select on v_$sql_plan to scott; OR SELECT_CATALOG role or select any dictionary system privilege For dbms_xplan.display_awr grant select on dba_hist_sqltext to scott grant select on dba_hist_sql_plan to scott; grant select on v_$database to scott; OR SELECT_CATALOG role
  • 14.
    Really complicated recursiveSQL statements! 14 Internals of dbms_xplan select * from (table(dbms_xplan.display_cursor('8gzkcsvw362s3',2,'allstats')); select /* EXEC_FROM_DBMS_XPLAN */ case when upper(sql_text) like '%DBMS_XPLAN%' then 0 else 1 end case, SQL_ID, child_number from v$sql where SQL_ID ='8gzkcsvw362s3' and child_number =2 SELECT PLAN_TABLE_OUTPUT FROM TABLE(CAST(DBMS_XPLAN.PREPARE_RECORDS(:B1 , :B2 ) AS SYS.DBMS_XPLAN_TYPE_TABLE)) SELECT /*+ opt_param('parallel_execution_enabled', 'false') */ extractvalue(xmlval, '/*/info[@type = "sql_profile"]'), extractvalue(xmlval, '/*/info[@type = "sql_patch"]'), extractvalue(xmlval, '/*/info[@type = "baseline"]'), extractvalue(xmlval, '/*/info[@type = "outline"]'), extractvalue(xmlval, '/*/info[@type = "dynamic_sampling"]'), extractvalue(xmlval, '/*/info[@type = "dop"]'), extractvalue(xmlval, '/*/info[@type = "dop_reason"]'), extractvalue(xmlval, '/*/info[@type = "queuing_reason"]'), extractvalue(xmlval, '/*/info[@type = "row_shipping"]') , extractvalue(xmlval, '/*/info[@type = "index_size"]'), extractvalue(xmlval, '/*/info[@type = "result_checksum"]'), extractvalue(xmlval, '/*/info[@type = "cardinality_feedback"]'), extractvalue(xmlval, '/*/info[@type = "xml_suboptimal"]'), extractvalue(xmlval,'/*/info[@type = "plan_hash"]') from (select xmltype(:v_other_xml) xmlval from dual)
  • 15.
    15 More internals SELECT /*+ opt_param('parallel_execution_enabled', 'false') */ /* EXEC_FROM_DBMS_XPLAN */ id, position, depth , operation, options, object_name, cardinality, bytes, temp_space, cost, io_cost, cpu_cost, time, …. vp.optimal_executions opt_cnt, vp.onepass_executions one_cnt, vp.multipasses_executions multi_cnt, vp.max_tempseg_size max_tmp, vp.last_tempseg_size last_tmp from V$SQL_PLAN_STATISTICS_ALL vp, v$sql where vp.SQL_ID = '8gzkcsvw362s3' and vp.child_number=2 and vp.SQL_ID = v$sql.SQL_ID and v$sql.child_number=2) order by id
  • 16.
    16 How doI tune?  Prepare the sql to be run for performance analysis. my_sql.sql Set linesize 300; set pagesize 1000; --Declare variable and assign values var order_id number; execute :order_id:=53759119 SELECT oeh.header_id, oel.line_id FROM oe_order_headers_all oeh, oe_order_lines_all oel WHERE oeh.header_id = :order_id AND oeh.header_id = oel.header_id / select * from table (dbms_xplan.DISPLAY_CURSOR(null, null, 'ALLSTATS')) /
  • 17.
    17 Do’s &Don’ts  Do’s 1. Current execution plan and runtime statistics are the first step. 2. Execute a test case first to reproduce.  Don’t 1. Try to use same bind type as application uses. - Literal vs bind variables - number vs varchar2 data type etc 2. Try to use format same as the application for your test case. - CTAS vs INSERT
  • 18.
    PLAN_TABLE_OUTPUT SQL_ID cttafpfjwqjdm,child number 0 ------------------------------------- select oeh.header_id,oel.line_id from oe_order_headers_all oeh,oe_order_lines_all oel where oeh.header_id=:order_id and oeh.header_id=oel.header_id Plan hash value: 4180984038 ------------------------------------------------------------------------------------------------------------------------- -- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop | ------------------------------------------------------------------------------------------------------------------------- -- | 0 | SELECT STATEMENT | | | | 11 (100)| | | | | 1 | NESTED LOOPS | | 6 | 114 | 11 (0)| 00:00:01 | | | | 2 | PARTITION HASH SINGLE | | 1 | 6 | 2 (0)| 00:00:01 | KEY | KEY | |* 3 | INDEX UNIQUE SCAN | OE_ORDER_HEADERS_U1 | 1 | 6 | 2 (0)| 00:00:01 | KEY | KEY | | 4 | TABLE ACCESS BY GLOBAL INDEX ROWID| OE_ORDER_LINES_ALL | 6 | 78 | 9 (0)| 00:00:01 | ROWID | ROWID | |* 5 | INDEX RANGE SCAN | OE_ORDER_LINES_N1 | 6 | | 3 (0)| 00:00:01 | | | ------------------------------------------------------------------------------------------------------------------------- -- 18 dbms_xplan.display_cursor
  • 19.
    ... Predicate Information(identified by operation id): --------------------------------------------------- 3 - access("OEH"."HEADER_ID"=:ORDER_ID) 5 - access("OEL"."HEADER_ID"=:ORDER_ID) Note ----- - Warning These are only collected when: * hint 'gather_plan_statistics' is used for the statement or * parameter 'statistics_level' is set to 'ALL', at session or system level * Cardinality feedback used * Dynamic sampling used 19 dbms_xplan.display_cursor ..2
  • 20.
    ------------------------------------------------------------------------------------------------------------------------ -- |Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop | ------------------------------------------------------------------------------------------------------------------------ --- | 0 | SELECT STATEMENT | | | | 11200 (100)| | | | | 1 | NESTED LOOPS | | 6 | 114 | 11 (0)| 00:10:01 | | | | 2 | PARTITION HASH SINGLE | | 1 | 6 | 2 (0)| 00:00:01 | KEY | KEY | |* 3 | INDEX UNIQUE SCAN | OE_ORDER_HEADERS_U1 | 1 | 6 | 2 (0)| 00:00:01 | KEY | KEY | |* 4 | TABLE ACCESS BY GLOBAL INDEX ROWID| OE_ORDER_LINES_ALL | 6 | 78 | 9000 (0)| 00:07:01 | ROWID | ROWID | |* 5 | INDEX RANGE SCAN | OE_ORDER_LINES_N1 | 60000 | | 300 (0)| 00:03:01 | | | ------------------------------------------------------------------------------------------------------------------------ --- Predicate Information (identified by operation id): --------------------------------------------------- 3 - access("OEH"."HEADER_ID"=:ORDER_ID) 4 – filter ("OEL".“OPEN_FLAG=’Y’) 5 - access("OEL"."HEADER_ID"=:ORDER_ID) 20 dbms_xplan: access and filter predicates Added a predicate oel.open_flag=‘Y’
  • 21.
    21 Detailed executionstatistics  v$sql_plan_statistics_all collects row source level execution statistics  ROWS  CPU  Physical IO  Logical IO  Elapsed time Setting statistics_level=‘ALL’ at system level can be resource intensive and should preferably not be enabled in busy PRODUCTION SYSTEM  To enable at session level set statistics_level=‘ALL’  To enable for all sessions set at system level statistics_level=‘ALL’  To set a SQL statement level add the hint  /*+ gather_plan_statistics */ in the statement.
  • 22.
    22 dbms_xplan: script  Modify the script to enable extended execution statistics --my_sql.sql script_name set linesize 300; set pagesize 1000; --Declare variable and assign values var order_id number; execute order_id:=53759119 alter session set statistics_level=‘ALL’; --OR ADD HINT SELECT /*+ gather_plan_statistics */ oeh.header_id, oel.line_id FROM oe_order_headers_all oeh, oe_order_lines_all oel WHERE oeh.header_id = :order_id AND oeh.header_id = oel.header_id /
  • 23.
    23 Execution statistics select * from table (dbms_xplan.DISPLAY_CURSOR(null, null, 'ALLSTATS LAST')) / SQL_ID 7gftgf917tg2x, child number 0 ------------------------------------- select /*+ gather_plan_statistics */ oeh.header_id,oel.line_id from oe_order_headers_all oeh,oe_order_lines_all oel where oeh.header_id=:order_id and oeh.header_id=oel.header_id Plan hash value: 4180984038 ------------------------------------------------------------------------------------------------------------------------------ | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | Reads | ------------------------------------------------------------------------------------------------------------------------------ | 0 | SELECT STATEMENT | | 1 | | 4 |00:00:00.03 | 12 | 11 | | 1 | NESTED LOOPS | | 1 | 6 | 4 |00:00:00.03 | 12 | 11 | | 2 | PARTITION HASH SINGLE | | 1 | 1 | 1 |00:00:00.01 | 3 | 3 | |* 3 | INDEX UNIQUE SCAN | OE_ORDER_HEADERS_U1 | 1 | 1 | 1 |00:00:00.01 | 3 | 3 | | 4 | TABLE ACCESS BY GLOBAL INDEX ROWID| OE_ORDER_LINES_ALL | 1 | 6 | 4 |00:00:00.02 | 9 | 8 | |* 5 | INDEX RANGE SCAN | OE_ORDER_LINES_N1 | 1 | 6 | 4 |00:00:00.01 | 5 | 4 | ------------------------------------------------------------------------------------------------------------------------------ Predicate Information (identified by operation id): --------------------------------------------------- 3 - access("OEH"."HEADER_ID"=:ORDER_ID) 5 - access("OEL"."HEADER_ID"=:ORDER_ID) 25 rows selected.
  • 24.
    24 Alias select* from table (dbms_xplan.DISPLAY_CURSOR(null, null, 'ALLSTATS LAST +alias -predicate')); SELECT /*+ gather_plan_statistics */ oel.line_id FROM oe_order_lines_all oel WHERE oel.open_flag = 'Y' and exists (select 1 from oe_order_headers_all oeh where oeh.header_id = oel.header_id and oeh.open_flag='Y' and oeh.last_update_date > sysdate -5) Plan hash value: 746840967 -------------------------------------------------------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | OMem | 1Mem | Used-Mem | -------------------------------------------------------------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 3 |00:00:00.01 | 16 | | | | | 1 | NESTED LOOPS | | 1 | | 3 |00:00:00.01 | 16 | | | | | 2 | NESTED LOOPS | | 1 | 1 | 3 |00:00:00.01 | 10 | | | | | 3 | SORT UNIQUE | | 1 | 1 | 1 |00:00:00.01 | 5 | 2048 | 2048 | 2048 (0)| | 4 | TABLE ACCESS BY GLOBAL INDEX ROWID| OE_ORDER_HEADERS_ALL | 1 | 1 | 1 |00:00:00.01 | 5 | | | | | 5 | INDEX RANGE SCAN | CCW_OE_ORD_HEADERS_ALL_D1 | 1 | 7 | 1 |00:00:00.01 | 4 | | | | | 6 | INDEX RANGE SCAN | OE_ORDER_LINES_N1 | 1 | 6 | 3 |00:00:00.01 | 5 | | | | | 7 | TABLE ACCESS BY GLOBAL INDEX ROWID | OE_ORDER_LINES_ALL | 3 | 1 | 3 |00:00:00.01 | 6 | | | | -------------------------------------------------------------------------------------------------------------------------------------------------------- Query Block Name / Object Alias (identified by operation id): ------------------------------------------------------------- 1 - SEL$5DA710D3 4 - SEL$5DA710D3 / OEH@SEL$2 5 - SEL$5DA710D3 / OEH@SEL$2 6 - SEL$5DA710D3 / OEL@SEL$1 7 - SEL$5DA710D3 / OEL@SEL$1
  • 25.
    SQL_ID cu2f3xhzy75vc, childnumber 0 ------------------------------------- SELECT /*+ gather_plan_statistics qb_name(outer_block) */ oel.line_id FROM oe_order_lines_all oel WHERE oel.open_flag = 'Y' and exists (select /*+ qb_name(innner_block) */ 1 from oe_order_headers_all oeh where oeh.header_id = oel.header_id and oeh.open_flag='Y' and oeh.last_update_date > sysdate -5); Plan hash value: 746840967 -------------------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | ..| --------------------------------------------------------------------------------------------------------------------.. | 0 | SELECT STATEMENT | | 1 | | 3 |00:00:00.01 | … Query Block Name / Object Alias (identified by operation id): ------------------------------------------------------------- 1 - SEL$8E94A21F 4 - SEL$8E94A21F / OEH@INNNER_BLOCK 5 - SEL$8E94A21F / OEH@INNNER_BLOCK 6 - SEL$8E94A21F / OEL@OUTER_BLOCK 7 - SEL$8E94A21F / OEL@OUTER_BLOCK 25 Query Block name
  • 26.
    26 Default QBName Prefix Row Source operation CRI$ Create index statement DEL$ DELETE statement INS$ Insert Statement MISC$ Miesc SQL like lock table MRG$ Merge Statement SEL$ SELECT statement SET$ Set operators UPD$ Update statement
  • 27.
    27 Hints orOutlines set linesize 300 set pagesize 300 alter session set statistics_level='ALL'; SELECT /* outline query */ RECID, ALC, FRC ... FROM ORD_AP_IF_TASK WHERE PROCESSED_FLAG = 'U') ORDER BY TABLENAME, CREATION_DATE; select * from table( dbms_xplan.display_cursor (null,null,'ALLSTATS LAST +outline')) /
  • 28.
    Outline Data ------------- /*+ BEGIN_OUTLINE_DATA IGNORE_OPTIM_EMBEDDED_HINTS OPTIMIZER_FEATURES_ENABLE('11.2.0.2') OPT_PARAM('_b_tree_bitmap_plans' 'false') OPT_PARAM('_fast_full_scan_enabled' 'false') ALL_ROWS OUTLINE_LEAF(@"SEL$2") OUTLINE_LEAF(@"SEL$1") FULL(@"SEL$3" "ORD_AP_IF_TASKS"@"SEL$3") INDEX_RS_ASC(@"SEL$2" "ORD_AP_IF_PROJECTS"@"SEL$2“ ("ORD_AP_IF_PROJECTS"."PROCESSED_FLAG")) END_OUTLINE_DATA */ 28 Outline --------------------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | … -------------------------------------------------------------------------------------------------------------------… | 0 | SELECT STATEMENT | | 1 | | 0 |00:00:27.40 | 153K| .. | 1 | SORT ORDER BY | | 1 | 2146K| 0 |00:00:27.40 | 153K| … | 2 | VIEW | | 1 | 2146K| 0 |00:00:27.40 | 153K| … | 3 | SORT UNIQUE | | 1 | 2146K| 0 |00:00:27.40 | 153K| … | 4 | UNION-ALL | | 1 | | 0 |00:00:27.40 | 153K| … | 5 | TABLE ACCESS BY INDEX ROWID| ORD_AP_IF_PROJECTS | 1 | 1 | 0 |00:00:00.01 | 3 | … | 6 | INDEX RANGE SCAN | ORD_AP_IF_PROJECTS_N1 | 1 | 1 | 0 |00:00:00.01 | 3 | | 7 | TABLE ACCESS FULL | ORD_AP_IF_TASKS | 1 | 2146K| 0 |00:00:27.40 | 153K| -------------------------------------------------------------------------------------------------------------------
  • 29.
    Outline Data ------------- /*+ Predicate Information (identified by operation id): --------------------------------------------------- 6 - access("PROCESSED_FLAG"='U') 7 - filter("PROCESSED_FLAG"='U') ... FULL(@"SEL$3" "ORD_AP_IF_TASKS"@"SEL$3") INDEX_RS_ASC(@"SEL$2" "ORD_AP_IF_PROJECTS "@"SEL$2" ("ORD_AP_IF_PROJECTS"."PROCESSED_FLAG")) END_OUTLINE_DATA */ 29 Tuning SQL SQLPLUS> select count(1) from ORD_AP_IF_TASKS where PROCESSED_FLAG='U'; COUNT(1) ---------- 0 There is an index on ORD_AP_IF_TASKS.PROCESSED_FLAG
  • 30.
    set linesize 300 set pagesize 300 alter session set statistics_level='ALL'; SELECT /*+ Copying outline as hint; Altering Full Table Scan to Index Range Scan. BEGIN_OUTLINE_DATA IGNORE_OPTIM_EMBEDDED_HINTS OPTIMIZER_FEATURES_ENABLE('11.2.0.2') DB_VERSION('11.2.0.2') OPT_PARAM('_b_tree_bitmap_plans' 'false') OPT_PARAM('_fast_full_scan_enabled' 'false') ALL_ROWS OUTLINE_LEAF(@"SEL$2") OUTLINE_LEAF(@"SEL$3") OUTLINE_LEAF(@"SET$1") OUTLINE_LEAF(@"SEL$1") NO_ACCESS(@"SEL$1" "from$_subquery$_001"@"SEL$1") INDEX_RS_ASC(@"SEL$3" “ORD_AP_IF_TASKS"@"SEL$3" (“ORD_AP_IF_TASKS"."PROCESSED_FLAG")) INDEX_RS_ASC(@"SEL$2" “ORD_AP_IF_PROJECTS"@"SEL$2" (“ORD_AP_IF_PROJECTS"."PROCESSED_FLAG")) END_OUTLINE_DATA */ WHERE PROCESSED_FLAG = 'U') ORDER BY TABLENAME, CREATION_DATE / select * from table(dbms_xplan.display_cursor (null,null,'ALLSTATS LAST +outline')) / 30 Bob the Builder FULL(@"SEL$3" "ORD_AP_IF_TASKS"@"SEL$3")
  • 31.
    Tuned Plan ---------------------------------------------------------------------------------------------------------… | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | --------------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 0 |00:00:00.01 | | 1 | SORT ORDER BY | | 1 | 2146K| 0 |00:00:00.01 | | 2 | VIEW | | 1 | 2146K| 0 |00:00:00.01 | | 3 | SORT UNIQUE | | 1 | 2146K| 0 |00:00:00.01 | | 4 | UNION-ALL | | 1 | | 0 |00:00:00.01 | | 5 | TABLE ACCESS BY INDEX ROWID| ORD_AP_IF_PROJECTS | 1 | 1 | 0 |00:00:00.01 | |* 6 | INDEX RANGE SCAN | ORD_AP_IF_PROJECTS_N1 | 1 | 1 | 0 |00:00:00.01 | | 7 | TABLE ACCESS BY INDEX ROWID| ORD_AP_IF_TASKS | 1 | 2146K| 0 |00:00:00.01 | |* 8 | INDEX RANGE SCAN | ORD_AP_IF_TASKS_N1 | 1 | 2173K| 0 |00:00:00.01 | ---------------------------------------------------------------------------------------------------------… Outline Data ------------- 31 /*+ BEGIN_OUTLINE_DATA IGNORE_OPTIM_EMBEDDED_HINTS OPT_PARAM('_b_tree_bitmap_plans' 'false') OPT_PARAM('_fast_full_scan_enabled' 'false') ALL_ROWS OUTLINE_LEAF(@"SEL$1") NO_ACCESS(@"SEL$1" "from$_subquery$_001"@"SEL$1") INDEX_RS_ASC(@"SEL$3" “ORD_AP_IF_TASKS"@"SEL$3" (“ORD_A__IF_TASKS"."PROCESSED_FLAG")) INDEX_RS_ASC(@"SEL$2" “ORD_AP_IF_PROJECTS"@"SEL$2" (“ORD_AP_IF_PROJECTS"."PROCESSED_FLAG")) END_OUTLINE_DATA */ Predicate Information (identified by operation id): --------------------------------------------------- 6 - access("PROCESSED_FLAG"='U') 8 - access("PROCESSED_FLAG"='U’)
  • 32.
    So many details..Solittle space.. Column Description Always available columns id Identified of each step in the execution plan; if prefixed with * then predicate information available in predicate section Operation Row source operation Name The database object in the operation CBO parse time information Rows Estimated number of rows returned by the row source operation; derived from statistics on names object in the operation Bytes Estimated amount of data returned by the operation TempSpc The estimated amount of temp space usage by the operation Cost(%CPU) The estimated cost of the row source operation. The percentage CPU cost is given in () for individual row source operation Time Estimated amount of time needed to execute that operation in HH:MM:SS Partitioning Pstart Number of first partition to be accessed Pstop The number of last partition to be accessed Parallel Processing TQ Table queue used for processing IN-OUT The relation between parallel operations PQ Distrib The distribution used by producers to send data to consumers Runtime Statistics Starts The number of times operation was executed (check more nested loop joins operation) A-Rows Actual number of rows returned A-Time Actual amount of time spent executing the operation I/O Statistics Buffers Logical reads operations performed during execution of each step Read Physical reads performed for each operation Write Physical writes performed 32
  • 33.
    33 dbms_xplan.display_awr Displays plans stored in AWR; Format select * from table(dbms_xplan.display_awr(‘sql_id’,plan_hash_value,db_id,’format’)); -plan_hash_value: to select a specific plan -dbid : specifies which database to select from Example script: SELECT * FROM TABLE( dbms_xplan.display_awr('&&sql_id', '&plan_hash_value', NULL, 'ALL +peeked_binds') );
  • 34.
    34 dbms_xplan.display_awr select* from table(dbms_xplan.display_awr('4jtbgawt37mcd',null, null, 'ALL +peeked_binds')); SQL_ID 4jtbgawt37mcd -------------------- Plan hash value: 327243540 --------------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | --------------------------------------------------------------------------------------------------------------- Peeked Binds (identified by position): -------------------------------------- 1 - :B3 (NUMBER): 7394 2 - :B2 (VARCHAR2(30), CSID=871): 'AAL' 3 - :B1 (VARCHAR2(30), CSID=871): '73057' SQL_ID 4jtbgawt37mcd -------------------- Plan hash value: 2294473928 --------------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | --------------------------------------------------------------------------------------------------------------- Peeked Binds (identified by position): -------------------------------------- 1 - :B3 (NUMBER): 9649 2 - :B2 (VARCHAR2(30), CSID=871): 'ZXU' 3 - :B1 (VARCHAR2(30), CSID=871): 'U5152'
  • 35.
    Cardinality feedback select/*+ gather_plan_statistics */ max(length(v1)) from order_headers_all where processed_flag='N' --------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | --------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 1 | | 1 | SORT AGGREGATE | | 1 | 1 | 1 | |* 2 | TABLE ACCESS FULL| ORDER_HEADERS_ALL | 1 | 50000 | 10 | --------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - filter("PROCESSED_FLAG"='N') ©OraInternals Riyaj Shamsudeen 35 Plan hash value: 872302569 Demo @demo_oh1.sql
  • 36.
    /*+ no_rewrite gather_plan_statistics*/ MAX(LENGTH(oh.v1)), MAX(LENGTH(oh.v1)) FROM order_headers_all oh WHERE EXISTS ( SELECT 1 FROM order_lines_all ol WHERE oh.order_id = ol.order_id AND line_processed_flag = 'Y' AND rownum >=1 AND oh.processed_flag='N' ; ©OraInternals Riyaj Shamsudeen 36 Starts SELECT ) Demo @demo_oh2.sql How many times did the EXISTS Subquery was executed?
  • 37.
    ALLSTATS LAST select* from table (dbms_xplan.display_cursor ('', '','ALLSTATS LAST')) ---------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | ---------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 1 | | 1 | SORT AGGREGATE | | 1 | 1 | 1 | |* 2 | FILTER | | 1 | | 10 | |* 3 | TABLE ACCESS FULL | ORDER_HEADERS_ALL | 1 | 50000 | 10 | | 4 | COUNT | | 10 | | 10 | |* 5 | FILTER | | 10 | | 10 | |* 6 | TABLE ACCESS BY INDEX ROWID| ORDER_LINES_ALL | 10 | 1 | 10 | |* 7 | INDEX RANGE SCAN | OL_N1 | 10 | 1 | 10 | ---------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - filter( IS NOT NULL) 3 - filter("OH"."PROCESSED_FLAG"='N') 5 - filter(ROWNUM>=1) 6 - filter("LINE_PROCESSED_FLAG"='Y') 7 - access("OL"."ORDER_ID"=:B1) ©OraInternals Riyaj Shamsudeen 37 Demo @demo_oh2.sql
  • 38.
    Starts ..2 select* from table (dbms_xplan.display_cursor ('', '','ALLSTATS')) SELECT 1 FROM PA_TASKS WHERE TASK_ID = :B1 ©OraInternals Riyaj Shamsudeen 38 Plan hash value: 357090087 -------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | -------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 256K| | 246K| |* 1 | INDEX UNIQUE SCAN| PA_TASKS_U1 | 256K| 1 | 246K| -------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 1 - access("TASK_ID"=:B1) How many times did we execute this statement?
  • 39.
    Cardinality feedback ..2 select * from table (dbms_xplan.display_cursor ('', '','ALLSTATS')) ------------------------------------------------------------------------------------------ | Id | Operation | Name | Starts | E-Rows | A-Rows | ------------------------------------------------------------------------------------------ | 0 | UPDATE STATEMENT | | 7822 | | 0 | | 1 | UPDATE | ENI_OLTP_ITEM_STAR | 7822 | | 0 | |* 2 | FILTER | | 7824 | | 7254K| |* 3 | TABLE ACCESS BY ROWID RANGE| ENI_OLTP_ITEM_STAR | 7823 | 69121 | 7256K| | 4 | TABLE ACCESS BY INDEX ROWID | MTL_SYSTEM_ITEMS_B | 7171K| 1 | 7167K| |* 5 | INDEX UNIQUE SCAN | MTL_SYSTEM_ITEMS_B_U1 | 7176K| 1 | 7172K| ------------------------------------------------------------------------------------------ ©OraInternals Riyaj Shamsudeen 39
  • 40.
    Cardinality feedback ..3 select * from table (dbms_xplan.display_cursor ('', '','ALLSTATS')) ------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | A-Time | Buffers | Reads | ------------------------------------------------------------------------------------------------------- | 0 | UPDATE STATEMENT | | 7822 |00:47:24.86 | 56M| 1082K| | 1 | UPDATE | ENI_OLTP_ITEM_STAR | 7822 |00:47:24.86 | 56M| 1082K| |* 2 | FILTER | | 7824 |00:01:27.46 | 23M| 868 | |* 3 | TABLE ACCESS BY ROWID RANGE| ENI_OLTP_ITEM_STAR | 7823 |00:01:23.30 | 23M| 868 | | 4 | TABLE ACCESS BY INDEX ROWID | MTL_SYSTEM_ITEMS_B | 7171K|00:41:09.13 | 25M| 1028K| |* 5 | INDEX UNIQUE SCAN | MTL_SYSTEM_ITEMS_B_U1 | 7176K|00:01:17.74 | 17M| 488 | ------------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - filter(CHARTOROWID(:B2)<=CHARTOROWID(:B1)) 3 - access(ROWID>=CHARTOROWID(:B2) AND ROWID<=CHARTOROWID(:B1)) 5 - access("MTI"."INVENTORY_ITEM_ID"=:B1 AND "MTI"."ORGANIZATION_ID"=:B2) ©OraInternals Riyaj Shamsudeen 40
  • 41.
    SQL - remote (SELECT /*+ materialize */ order_id FROM oli_table@orcl2 ol WHERE line_processed_flag='Y' ) SELECT /*+ no_rewrite gather_plan_statistics */ MAX(LENGTH(oh.v1)) FROM order_headers_all oh (SELECT 1 FROM rem1 WHERE oh.order_id = rem1.order_id ) AND oh.processed_flag='N' ; ©OraInternals Riyaj Shamsudeen 41 WITH rem1 AS WHERE EXISTS Demo @demo_oh3.sql
  • 42.
    Remote queries --------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | --------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 1 | | 1 | TEMP TABLE TRANSFORMATION | | 1 | | 1 | | 2 | LOAD AS SELECT | | 1 | | 0 | | 3 | REMOTE | OLI_TABLE | 1 | 100K| 100K| | 4 | SORT AGGREGATE | | 1 | 1 | 1 | |* 5 | HASH JOIN RIGHT SEMI | | 1 | 50000 | 10 | | 6 | VIEW | | 1 | 100K| 100K| | 7 | TABLE ACCESS FULL | SYS_TEMP_0FD9FC884_E8A367F2 | 1 | 100K| 100K| |* 8 | TABLE ACCESS FULL | ORDER_HEADERS_ALL | 1 | 50000 | 10 | --------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 5 - access("OH"."ORDER_ID"="REM1"."ORDER_ID") 8 - filter("OH"."PROCESSED_FLAG"='N') … Remote SQL Information (identified by operation id): ---------------------------------------------------- 3 - SELECT /*+ */ "ORDER_ID","LINE_PROCESSED_FLAG" FROM "OLI_TABLE" "OL" WHERE LINE_PROCESSED_FLAG"='Y' (accessing ©OraInternals Riyaj Shamsudeen 42 ‘ORCL2.ORACLE.com' ) Demo @demo_oh3.sql ADVANCED option provides remote query output
  • 43.
    SQL – remote..2 /*+ no_rewrite gather_plan_statistics use_nl (oh ol) */ MAX(LENGTH(oh.v1)) FROM order_headers_all oh, (SELECT order_id FROM oli_table@orcl2 ol WHERE line_processed_flag='Y' ) ol WHERE oh.order_id = ol.order_id AND oh.processed_flag='N' ; ©OraInternals Riyaj Shamsudeen 43 SELECT Demo @demo_oh3.sql
  • 44.
    Remote queries (2) ------------------------------------------------------------------------------------ | Id | Operation | Name | Rows | Bytes | Cost (%CPU)|IN-OUT| ------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | | | 100K(100)| | | 1 | SORT AGGREGATE | | 1 | 223 | | | | 2 | NESTED LOOPS | | 50000 | 10M| 100K (1)| | |* 3 | TABLE ACCESS FULL| ORDER_HEADERS_ALL | 50000 | 9M| 403 (7)| | | 4 | REMOTE | OLI_TABLE | 1 | 15 | 2 (0)| R->S | ------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 3 - filter("OH"."PROCESSED_FLAG"='N') Remote SQL Information (identified by operation id): ---------------------------------------------------- 4 - SELECT /*+ USE_NL ("OL") */ "ORDER_ID", "LINE_PROCESSED_FLAG" FROM "OLI_TABLE" "OL" WHERE "LINE_PROCESSED_FLAG"='Y' AND :1="ORDER_ID“ (accessing ‘ORCL2.ORCL.COM' ) ©OraInternals Riyaj Shamsudeen 44 Demo @demo_oh5.sql
  • 45.
    Parallel Queries ---------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | ---------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 1 |00:00:08.83 | | 1 | SORT AGGREGATE | | 1 | 1 | 1 |00:00:08.83 | |* 2 | HASH JOIN | | 1 | 999K| 260K|00:00:08.76 | | 3 | VIEW | | 1 | 999K| 999K|00:00:02.11 | |* 4 | COUNT STOPKEY | | 1 | | 999K|00:00:01.52 | | 5 | PX COORDINATOR | | 1 | | 999K|00:00:00.84 | | 6 | PX SEND QC (RANDOM) | :TQ10000 | 0 | 11M| 0 |00:00:00.01 | |* 7 | COUNT STOPKEY | | 0 | | 0 |00:00:00.01 | | 8 | PX PARTITION HASH ALL| | 0 | 11M| 0 |00:00:00.01 | | 9 | INDEX FULL SCAN | OE_ORDER_HEADERS_U1 | 0 | 11M| 0 |00:00:00.01 | | 10 | VIEW | | 1 | 999K| 999K|00:00:02.28 | |* 11 | COUNT STOPKEY | | 1 | | 999K|00:00:01.68 | | 12 | INDEX FULL SCAN | OE_ORDER_LINES_N1 | 1 | 57M| 999K|00:00:00.98 | ---------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - access("OH"."HEADER_ID"="OL"."HEADER_ID") 4 - filter(ROWNUM<1000000) 7 - filter(ROWNUM<1000000) 11 - filter(ROWNUM<1000000) ©OraInternals Riyaj Shamsudeen 45 Note ----- - Degree of Parallelism is 8 because of hint ALLSTATS LAST Also, notice the broken cardinality Feedback.
  • 46.
    Parallel Queries After1 execution with DOP=8 --------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | ---------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 1 |00:00:08.83 | | 1 | SORT AGGREGATE | | 1 | 1 | 1 |00:00:08.83 | |* 2 | HASH JOIN | | 1 | 999K| 260K|00:00:08.76 | | 3 | VIEW | | 1 | 999K| 999K|00:00:02.11 | |* 4 | COUNT STOPKEY | | 1 | | 999K|00:00:01.52 | | 5 | PX COORDINATOR | | 1 | | 999K|00:00:00.84 | | 6 | PX SEND QC (RANDOM) | :TQ10000 | 0 | 11M| 0 |00:00:00.01 | |* 7 | COUNT STOPKEY | | 8 | | 1072K|00:00:03.83 | | 8 | PX PARTITION HASH ALL| | 8 | 11M| 1072K|00:00:03.17 | | 9 | INDEX FULL SCAN | OE_ORDER_HEADERS_U1 | 8 | 11M| 1072K|00:00:02.56 | | 10 | VIEW | | 1 | 999K| 999K|00:00:02.28 | |* 11 | COUNT STOPKEY | | 1 | | 999K|00:00:01.68 | | 12 | INDEX FULL SCAN | OE_ORDER_LINES_N1 | 1 | 57M| 999K|00:00:00.98 | ---------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - access("OH"."HEADER_ID"="OL"."HEADER_ID") 4 - filter(ROWNUM<1000000) 7 - filter(ROWNUM<1000000) 11 - filter(ROWNUM<1000000) ©OraInternals Riyaj Shamsudeen 46 Note ----- - Degree of Parallelism is 8 because of hint ALLSTATS
  • 47.
    Parallel Queries After4 executions with DOP=16 ---------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | ---------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 4 | | 4 |00:00:38.25 | | 1 | SORT AGGREGATE | | 4 | 1 | 4 |00:00:38.25 | |* 2 | HASH JOIN | | 4 | 999K| 418K|00:00:38.16 | | 3 | VIEW | | 4 | 999K| 3999K|00:00:07.67 | |* 4 | COUNT STOPKEY | | 4 | | 3999K|00:00:05.53 | | 5 | PX COORDINATOR | | 4 | | 3999K|00:00:03.12 | | 6 | PX SEND QC (RANDOM) | :TQ10000 | 0 | 11M| 0 |00:00:00.01 | |* 7 | COUNT STOPKEY | | 64 | | 4779K|00:00:56.27 | | 8 | PX PARTITION HASH ALL| | 64 | 11M| 4779K|00:00:53.19 | | 9 | INDEX FULL SCAN | OE_ORDER_HEADERS_U1 | 64 | 11M| 4779K|00:00:50.33 | | 10 | VIEW | | 4 | 999K| 3999K|00:00:14.59 | |* 11 | COUNT STOPKEY | | 4 | | 3999K|00:00:12.32 | | 12 | PX COORDINATOR | | 4 | | 3999K|00:00:09.35 | | 13 | PX SEND QC (RANDOM) | :TQ20000 | 0 | 57M| 0 |00:00:00.01 | |* 14 | COUNT STOPKEY | | 64 | | 4169K|00:05:45.40 | | 15 | PX BLOCK ITERATOR | | 64 | 57M| 4169K|00:05:42.68 | |* 16 | TABLE ACCESS FULL | OE_ORDER_LINES_ALL | 233 | 57M| 4169K|00:05:26.98 | ---------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- .. ©OraInternals Riyaj Shamsudeen 47 Note ----- - Degree of Parallelism is 16 because of hint ALLSTATS
  • 48.
    ©OraInternals Riyaj Shamsudeen48 Note section Note ----- - dynamic sampling used for this statement (level=2) Note ----- - SQL profile “SQL_PROF_4awcsbtwr8ksz" used for this statement Note ----- - Cardinality feedback used
  • 49.
    Few limitations Display_awr does not store predicates.  Of course , not all SQL statements are stored in AWR repository (color important statements).  Display_cursor is not RAC aware. You can query the plans only from the local instances using display_cursor.  Run time statistics are printed only after the completion of SQL statements (Think production long running queries). ©OraInternals Riyaj Shamsudeen 49
  • 50.
    ©OraInternals Riyaj Shamsudeen50 SQL monitor SET LONG 1000000 SET LONGCHUNKSIZE 1000000 SET LINESIZE 1000 SET PAGESIZE 0 SET TRIM ON SET TRIMSPOOL ON SET ECHO OFF SET FEEDBACK OFF SELECT DBMS_SQLTUNE.report_sql_monitor( sql_id => '&sql_id', type=>'TEXT' , report_level => 'ALL') from dual /
  • 51.
  • 52.
    Output ..2 ©OraInternalsRiyaj Shamsudeen 52
  • 53.
    53 A Presentationsponsored by
  • 54.
    ©OraInternals Riyaj Shamsudeen54 Riyaj Shamsudeen  19 years using Oracle products/DBA  OakTable member  Oracle ACE Director  Certified DBA versions 7.0,7.3,8,8i,9i &10g  Specializes in RAC, performance tuning, Internals and E-business suite  Chief DBA with OraInternals  Co-author few books  Email: rshamsud@orainternals.com  Blog : orainternals.wordpress.com  Web: www.orainternals.com
  • 55.
    Thank you forattending! If you like this presentation, you will love my 2-part intensive, online RAC webinar. http://www.orainternals.com/training/advanced-rac-training Email: rshamsud@gmail.com Week Dates Time Week1 TBA 8AM – 2PM PDT Week 2 TBA 8AM - 2PM PDT ©OraInternals Riyaj Shamsudeen 55
  • 56.
    ©OraInternals Riyaj Shamsudeen56 References • Oracle support site. Metalink.oracle.com. Various documents • Troubleshooting Oracle performance - Christian Antongini • http://www.orainternals.com/papers - Riyaj Shamsudeen • Various article from web led through on google search • Tom Kyte’s website Asktom.oracle.com

Editor's Notes

  • #4 Explain plan: Execute EXPLAIN PLAN for the SQL and query plan_table output It’s a calculated/ estimated plan No bind variable peeking, not reliable No execution of the statement Auto Trace: Uses explain plan internally hence no extra benefit SQL_Trace: Reliable but have to enable trace and use tkprof; both don’t easily provide the complete picture about SQL execution DBA_HIST_SQL_PLAN (historical plans) Actual executed plan Provides more detailed runtime and parse information about the SQL execution Use DBMS_XPLAN
  • #9 SQL Trace: Mostly used to find expensive queries in a session (using sort options) Trace need to be enabled for the session at 4,8 or level 12 Tkprof of raw trace needed to start tuning Doesn’t show the CBO analysis done at parse time No predicate information DBMS_XPLAN Gives information on CBO analysis at parse time Row source level runtime statistics shown Predicate information shown upfront No need to enable any kind of trace Easy to get the output Has number of options available to show lot more details like bind variable values, CBO information in notes section, runtime execution statistics etc. Provides function to get history of plans for the SQL_ID from AWR repo
  • #18 Do’s Always try to execute the query to see how its performing as the first step Real time execution plan and runtime statistics should be the first step of solving any sql tuning issue Don’t Never change the bind variable with literal value to check the execution plan and runtime statistics As much possible run the SQL as the application will run it.