SPOW (Performance Optimization Workshop)

1

PerformanceOptimizationWorkshop

Kim, Ji Hoon

SAP - Active Global Support

February, 2008

SAP AG 2005, SAP Customer Program Optimization / 2

Agenda

Analyzing Tools

Database Access Optimization

Internal Table Optimization

Case Study

2

Analyzing Tools

SQL performance trace

ABAP runtime analysis

Analyzing transaction steps

Performance Optimization Examples in SAP system


Analyzing Transaction Steps: Overview

Database serverNetwork

NetworkApplication server

Presentation server

DispatcherQueue

Databasebuffer

Roll fileRoll file

R/3 databaseinterface

User context

. . .

R/3 work process

Dispatcher

R/3 table buffer

Databaseprocess

Roll buffer4

12

23 13

1

5

6 1011

7

9

8

3


Analyzing Transaction Steps: R/3 Workload Monitor


Analyzing Transaction Steps: Response Time

4

Analyzing Tools






SQL Performance Trace: Initial Screen

5


SQL Performance Trace: SQL Trace Overview

Application server

R/3 tablebuffering

SELECT <field list> FROM vvbakWHERE ...

R/3 databaseinterface

ABAP Program

Database server

Databaseprocess

Databasebuffer

data records

Data-basefiles

SQLTraceFile


SQL Performance Trace: Trace List

6


SQL Performance Trace: Database Operations

Applicationserver

SELECT Fieldlist FROM vvbakWHERE vbeln = ‘0000000100’.

ABAP Program

Databaseserver

SAP cursor cache DB cursor available,no or yes?

Data bufferDB SQL cacheSELECT mandt ...FROM VVBAKWHERE vbeln = :A1

Shared memory of the database server

DB cursor cache

A1

PREPAREin trace

OPENin trace

FETCHin trace

REOPENin trace

FETCHin trace

Database InterfaceDatarecords


SQL Performance Trace: Explain SQL

SQL Statement

SELECT"VBELN" , "AUART"

FROM"VVBAK"

WHERE"MANDT" = :A0 AND "VBELN" BETWEEN :A1 AND :A2

Execution Plan

SELECT STATEMENT ( Estimated Costs = 3 , Estimated #Rows = 3 )

TABLE ACCESS BY INDEX ROWID VVBAK

INDEX RANGE SCAN VVBAK~0

Explain with hint... Optimizer Trace Analyze...

System HelpShow Execution Plan for SQL Statement

Table VVBAK

Last statistics date 01.09.1999Analyze Method ComputeNumber of rows 1.000Number of blocks allocated 626Number of empty blocks 15Average space 7.328Chain count 0Average row length 454

UNIQUE Index VVBAK~0

Column Name #Distinct

MANDT 1VBELN 1.000

Index Statistics Analyze...

Table and Index Info for VVBAK

1

2

34

5

7


SQL Performance Trace: ABAP Display

Transaction = PID = 9551 Ptype = DIA Client = 100 User

Duration Object name Oper Rec RC Statement

41 VVBAP REOPEN 0 0 SELECT WHERE "MANDT" = '100' AND "VBEL805 VVBAP FETCH 5 140341 VVBAP REOPEN 0 0 SELECT WHERE "MANDT" = '100' AND "VBEL785 VVBAP FETCH 5 140341 VVBAP REOPEN 0 0 SELECT WHERE "MANDT" = '100' AND "VBEL788 VVBAP FETCH 5 140340 VVBAK REOPEN 0 0 SELECT WHERE "MANDT" = '100' AND "VBEL

1.061 VVBAK FETCH 10 14031.327 VVBAP PREPARE 0 0 SELECT WHERE "MANDT" = :A0 AND "VBELN"

85 VVBAP OPEN 0 0 SELECT WHERE "MANDT" = '100' AND "VBEL6.919 VVBAP FETCH 49 1403826 VBAK_VBAP PREPARE 0 0 SELECT WHERE "MANDT" = :A0 AND "VBELN"41 VBAK_VBAP OPEN 0 0 SELECT WHERE "MANDT" = '100' AND "VBEL

5.924 VBAK_VBAP FETCH 49 1403800 VVBAK PREPARE 0 0 SELECT WHERE ( T_01 . "MANDT" = :A0 A46 VVBAK OPEN 0 0 SELECT WHERE ( T_01 . "MANDT" = '100'

5.704 VVBAK FETCH 49 1403217 VVBAK REOPEN 0 0 SELECT WHERE "MANDT" = '100' AND "VBEL

DDIC info Explain SQL ABAP display Extended list Replace var. Sort

Trace Edit Goto System HelpBasic SQL list - sorted by PID

119 SELECT vbeln auart FROM vvbak120 INTO CORRESPONDING FIELDS OF TABLE g_itab_vvbak121 WHERE vbeln IN g_vbeln.122123 IF sy-subrc NE 0. EXIT. ENDIF. " Necessary for the WHERE124125 SELECT vbeln posnr matnr FROM vvbap126 INTO CORRESPONDING FIELDS OF TABLE g_itab_vvbap127 FOR ALL ENTRIES IN g_itab_vvbak128 WHERE vbeln = g_itab_vvbak-vbeln.

Active line 119

Note marked line

ABAP-Editor: Display Program SAPBC490D_SQL_LOGICAL_VIEWS


SQL Performance Trace: Compressed Summary

8


SQL Performance Trace: Identical selects

Executions

422222222222

Object name

VVBAKVVBAPVVBAPVVBAPVVBAPVVBAPVVBAPVVBAPVVBAPVVBAPVVBAPVVBAP

WHERE clause

"MANDT" = '100' AND "VBELN" BETWEEN '000000000"MANDT" = '100' AND "VBELN" = '0000000001'"MANDT" = '100' AND "VBELN" = '0000000002'"MANDT" = '100' AND "VBELN" = '0000000003'"MANDT" = '100' AND "VBELN" = '0000000004'"MANDT" = '100' AND "VBELN" = '0000000005'"MANDT" = '100' AND "VBELN" = '0000000006'"MANDT" = '100' AND "VBELN" = '0000000007'"MANDT" = '100' AND "VBELN" = '0000000008'"MANDT" = '100' AND "VBELN" = '0000000009'"MANDT" = '100' AND "VBELN" = '0000000010'"MANDT" = '100' AND "VBELN" = '0000000001' OR

Continue Cancel

System HelpIdentical selects

Analyzing Tools





9


ABAP Runtime Analysis: Overview

Application server

SET RUNTIME ANALYZER ONLOOP AT itab…ENDLOOPSET RUNTIME ANALYZER OFF

ABAP runtime environment

ABAPTraceFile

LocalTraceFile

The three phases of the ABAPruntime analysis:

Limiting the analysis

Obtaining the run data

Evaluating the results


ABAP Runtime Analysis: Initial Screen

MeasurementShort descriptionIn the current user session

TransactionProgramFunction module

Execute

In parallel mode

On / Off

Limit analysisVariant DEFAULT

Standard variant

Performance fileOther file

Tips & Tricks

Runtime analysis Edit Goto Utilities Settings System HelpRuntime analysis: Initial Screen

Runs the object in thecurrent user session

"On" causes thedata to be recordedin a separate user

session

10


ABAP Runtime Analysis: Aggregation

Program part statements Duration & type

Maximum size of fileMaximum execution time

FullPer calling positionNone

Aggregation

10001800

KBSeconds

No aggregationProgram part XStatement YDO 1000 TIMESProgram part X => 1001 EntriesStatement Y => 1001 Entries

ENDDO

Full aggregationProgram part XStatement YDO 1000 TIMESProgram part X => 1 EntryStatement Y => 1 Entry

ENDDO

Full aggregationProgram part XStatement YDO 1000 TIMESProgram part X => 1 EntryStatement Y => 1 Entry

ENDDO

Aggregation per calling itemProgram part XStatement YDO 1000 TIMESProgram part X => 2 EntriesStatement Y => 2 Entries

ENDDO

Aggregation per calling itemProgram part XStatement YDO 1000 TIMESProgram part X => 2 EntriesStatement Y => 2 Entries

ENDDO


ABAP Runtime Analysis: Evaluating the Results

Detailsview

Results displayscreen

Initialscreen

ABAPDBR/3

Statistics records:ConversionsLoaded programs

Calls Number Gross ...Runtime analysis 1 80,610LOOP 3 20,113...

• Select data file• Save data file locally• Evaluate the data

11


ABAP Runtime Analysis: Evaluating the Results (2)


ABAP Runtime Analysis: Evaluating the Results (3)

SELECT

PERFORM

READ TABLE

Gross Net

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12

Analyzing Tools






Performance Optimization Example in SAP system (1)

In any ABAP editor transactions (SE37, SE38, SE24, SE80, …)Menu PATH :

13


Performance Optimization Example in SAP system (2)


Single transaction analysis (ABAP + SQL Trace)

Transaction Code : ST12

14


Memory Analysis in ABAP debugger

Database Access OptimizationUnsuitable Access Path

Introduction to DB Indexes

Introduction to DB Joins

Changing the ABAP coding

Changing the Index Design

15


Overview: Cost-Based Database Optimizer

Cost-baseddatabaseoptimizer

ROWID MAND T VBELNPOSNR MATN R...

...4533 2 001

0000 132 4700030008 15...

...


...4433 9 001

0000 001 2200030047 11...

...


...4689 4 002

0000 965 800120001 23...

...

...


...4587 6 001

0000 001 2200130012 34...

...

Full table scan

Estimated costs

ROWID MANDT VBELNERDATERZETERNAM...

...65872 0010000123

...

Possible access pathsTable and indexstatistics

...

Index access

SELECT STATEMENT

VVBAKTABLE ACCESS FULL

SELECT STATEMENT

INDEX UNIQUE SCAN VVBAK~0

SELECT STATEMENT

INDEX RANGE SCAN VVBAK~0


Database

DBMS

Data bufferData buffer

DB SQL Cache

Database files

...

Database servermemory

R/3 workprocess

SELECT *FROM MARA

WHERE ...Logical read accesses

Physical read accesses

Data buffer

SQL statementswith access strategy

Data blocks (e.g. 8 KB blocks)

DB workprocess

Overview: DB SQL Cache

16


DB SQL Cache Analysis: Overview (2)

Appl.Server

Database system

ABAP program

R/3 DB interface

DBMSprocess

Database

Database buffer

Appl.Server

Database system

ABAP program

R/3 DB interface

DBMSprocess

Database

Database bufferLogical readaccesses

Physical readaccesses

Transferreddata records

Few recordsMany records

Many blocks Many blocks

Suitable access path No suitable access path


Search range(area of tablethat needs tobe searchedfor required

records)

Data recordscorresponding toWHERE clause

MANDT VBELN OBJNR ERNAM

001 000013245 654875454 ERNIE001 000013246 697935435 FRED001 000013247 673225747 JAMES001 000013248 216356543 GUS001 000013249 687535435 ERNIE001 000013250 258674802 KURT001 000113245 983231365 MAX001 000113251 522112486 BERT001 000113252 325348654 BERT002 000013249 241567685 HUGO002 000013250 968351332 FRED002 000013251 874352321 MAX002 000013252 544546546 GUS

Overview: Unsuitable Access Path

Narrowingthe search

17



001 000013245 654875454 ERNIE001 000013246 697935435 FRED001 000013247 673225747 JAMES001 000013248 216356543 GUSS001 000013249 687535435 ERNIE001 000013250 258674802 KURT001 000113245 983231365 MAX001 000113251 522112486 BERT001 000113252 325348654 BERT002 000013249 241567685 HUGO002 000013250 968351332 FRED002 000013251 874352321 MAX002 000013252 544546546 GUSS

Reducingrows to betransferred

Reducingcolumnsto betransferred

Data recordscorresponding toWHERE clause

Search range(area of table that

needs to besearched for

required records)

Columnscorresponding toSELECT clause

Overview: Suitable Access Path (1)


FETCH

FETCH

FETCH

FETCH


001 000013245 654875454 ERNIE001 000013246 697935435 FRED001 000013247 673225747 JAMES001 000013248 216356543 GUSS001 000013249 687535435 ERNIE001 000013250 258674802 KURT001 000113245 983231365 MAX001 000113251 522112486 BERT001 000113252 325348654 BERT002 000013249 241567685 HUGO002 000013250 968351332 FRED002 000013251 874352321 MAX002 000013252 544546546 GUSS

:

Reducing datatransfer

Data transfer toapplication server

Overview: Suitable Access Path (2)

18


Introduction to DB Index : Overview (1)



19


Introduction to DB Index : Index Unique Scan

’


Introduction to DB Index : Index Range Scan (1)

20


Introduction to DB Index : Index Range Scan (2)

POSNR



21


Introduction to DB Index : Concatenation


Full Table Scan

22


Table Access Strategies


DB2 example : Index Unique Scan

23


Oracle example : Index Unique Scan


DB2 example : Index Range Scan

24


Oracle example : Index Range Scan


DB2 example : Full Table Scan

25


Oracle example : Full Table Scan


DB2 example : Concatenation

26


Oracle example : Concatenation






27


Introduction to DB Joins : Overview

T1K1 F1 F2

T2K1 F3 F4

DBMS

T1.K1 T1.F1 T1.F2 T2.F3 T2.F4

Application

T1.K1 T1.F1 T1.F2 T2.F3 T2.F4T1.K1 T1.F1 T1.F2 T2.F3 T2.F4T1.K1 T1.F1 T1.F2 T2.F3 T2.F4T1.K1 T1.F1 T1.F2 T2.F3 T2.F4 Resulting set

Database

SELECT T1~K1 T1~K2 T1~F2 T2~F3 T2~F4FROM tab1 AS T1 INNER JOIN tab2 AS T2ON T1~K1 = T2~K1WHERE T1~F2 = value.ON

INNER JOINSELECT


Introduction to DB Joins : Nested Loop

MANDT VBELN OBJNR ...001 0000120 0000110001 0000121001 0000122 0000110001 0000123 0000777001 0000124 0000777001 0000125 0000777...


VVBAK VVBUK

MANDT VBELN ...001 0000121 ...001 0000122 ...

001 0000123 ...

...

MANDT VBELN ...001 0000121 ...001 0000122 ...

001 0000123 ...

...

Nested loop

SELECT t1~vbeln t2~vbobj INTO ...FROM vvbak AS t1 INNER JOIN vvbuk AS t2ON t1~vbeln = t2~vbelnWHERE t1~objnr = '0000777'.

28


Nested Loop

The top input to the nested loop is the outer table

The bottom input to the nested loop is the inner table

For each outer row, searches for matching rows are in the inner

input table

Effective if the outer input is very small and the inner input is

preindexed and very large

Optimizer sometimes sorts the outer input to improve locality of

the searches on the index over the inner input

Best when search uses an index (indexes on join columns are

used)

Low memory requirement


DB2 Nested Loop

29


Oracle Nested Loop


Introduction to DB Joins : Sort Merge Join

SELECT t1~vbeln t2~vbobj INTO ...FROM vvbap AS t1 INNER JOIN vvbak AS t2ON t1~vbeln = t2~vbelnWHERE t1~cuobj = ’12345’AND t2~objnr = ‘0000777’.



MANDT VBELN CUOBJ ...001 0000121 1 ...001 0000122 2 ...001 0000123 3 ...001 0000123 4 ......

001 0000123 12345 ...001 0000456 12345 ...

MANDT VBELN CUOBJ ...001 0000121 1 ...001 0000122 2 ...001 0000123 3 ...001 0000123 4 ......

001 0000123 12345 ...001 0000456 12345 ...

VVBAP VVBAK

Selection andmerging of

table records

Sort merge join

30


Sort Merge Join

Both inputs should be sorted on the merge column keys

An index on a correct set of columns is useful

A many-to-many merge join uses a temporary table to store rows

Very fast if the data that you want can be obtained presorted fromexisting B-tree indexes


DB2 Sort Merge Join

31


Oracle Sort Merge Join


Nested loopDecide which tables to use for accessAccess to next innermost table using JOIN condition

Sort Merge JoinEvaluate WHERE clause on all relevant tablesSort according to JOIN condition

Merge resulting set

Important Access Strategies for DB Joins

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SELECT bukrs belnr gjahrFROM bkkpfINTO TABLE g_itab_bkkpfWHERE belnr = ‘0000000100’.

ineffective use of indexineffective use of index

effective use of indexeffective use of index

SELECT bukrs belnr gjahrFROM bkkpfINTO TABLE g_itab_bkkpfWHERE bukrs = ‘0001’AND belnr = ‘0000000100’.

specific index fields: MANDT, BELNR=> gap in index search string

Index search string:‘001____0000000100’

specific index fields: MANDT, BUKRS, BELNR=> index fields specified fully

Index search string: ‘00100010000000100’WHERE bukrs

Missing WHERE Conditions (1)

33


SELECT vbeln erdat FROM vvbakCLIENT SPECIFIEDINTO TABLE g_itab_vvbakWHERE vbeln = ‘0000000100’.

ineffective use of indexineffective use of index

effective use of indexeffective use of index

SELECT vbeln erdat FROM vvbakINTO TABLE g_itab_vvbakWHERE vbeln = ‘0000000100’.

* orSELECT vbeln erdat FROM vvbakCLIENT SPECIFIEDINTO TABLE g_itab_vvbakWHERE mandt = sy-mandtAND vbeln = ‘0000000100’.

specific index fields: VBELN=> index fields not specified

Index search string: ‘___0000000100’

specific index fields: MANDT,VBELN

=> index fields specified fullyIndex search string: ‘0010000000100’

CLIENT SPECIFIED

WHERE vbeln

CLIENT SPECIFIED

WHERE mandt

Missing WHERE Conditions (2)


Critical Operators (NOT and <>)

SELECT vbeln bstnk kunnr FROM vvbakINTO TABLE g_itab_vvbakWHERE kunnr = '0000000050'AND NOT faksk = '00'.

SELECT vbeln bstnk kunnr FROM vvbakINTO TABLE g_itab_vvbakWHERE kunnr = '0000000050'AND faksk IN ('01','02','03','04','05','08','09').

Negative formulationNegative formulation

Positive formulationPositive formulation

specific index fields: MANDT,KUNNR and FAKSK => ineffective

useof indexes

IN

NOT

specific index fields: MANDT,KUNNR and FAKSK => effective use

of indexes

34


SELECT vbeln erdat erzet FROM vvbak INTO TABLE g_itab_vvbakWHERE vbeln BETWEEN '0000000001' AND '0000000005'.

SELECT vbeln erdat erzet FROM vvbak INTO TABLE g_itab_vvbakWHERE vbeln IN ('0000000001', '0000000002', '0000000003',

'0000000004', '0000000005').

BETWEEN operatorBETWEEN operator

IN operatorIN operatorReplace WHERE field LIKE value

withWHERE field = value

OmitWHERE field LIKE '%'

BETWEEN

IN

Critical Operators (BETWEEN)


Sort at Database Level or in ABAP?

35







SQL statements from SAP programs:Look for R/3 Notes

SQL statements from customer-owned programs:Avoid additional indexes on transaction data

Change existing indexes

If necessary, delete existing indexes

No secondary indexes on R/3 basis tablesTables with D010, D020, DD* or NAST

Prerequisites for Changing the Index Design

36


General rulesPrefer disjunctive indexes

No unintentionally used indexes

As few indexes as possible per table (as few as possible, but as many asnecessary)

Selection of index fieldsAs few fields as possible in index

As selective fields as possible in index

Selective fields as near to the beginning as possible

Do not change SAP standard indexesunless recommended by SAP (see SAP Note System)

Rules for Changing the Index Design


Selectivity Analysis: Semantic Typing

37


Selectivity Analysis: Distinct Values

30.09.1999 14:46:44 KP6 pwdf0024VVBAK

Data from DBA_TAB_COLUMNS

DatabaseLast Sample Distinct

Column Data type analyzed* size* values*

MANDT VARCHAR2 30.09.1999 220,780 1VBELN VARCHAR2 30.09.1999 220,780 220,780ERDAT VARCHAR2 30.09.1999 220,780 856

Back Table <-> Indices Extents Table columns Detailed analysis History Sort

Database analysis Goto Monitor System HelpTables and Indexes Columns of Table VVBAK

ERZET VARCHAR2 30.09.1999 220,780 187,023ERNAM VARCHAR2 30.09.1999 220,780 73ANGDT VARCHAR2 30.09.1999 220,780 435BNDDT VARCHAR2 30.09.1999 220,780 267

Updated by “ORACLE STATISTICS UPDATE”


Selectivity Analysis: Histograms (1)

38


DB05: Selectivity Analysis: Histograms (2)

Date/time of analysis: 02.08.1999 17:45:28Analyzed table: COSSTotal number of rows: 635,336 rowsRequested bytes per row: 31 bytes per rowRequested bytes to be buffered 100%: 19,695,416 bytesCurrent buffering mode: no buffering

USPOB

Key fields

Rows pergeneric key

GJAHRWRTTP

VERSN

Number of areas that are specified by generic key and contain the given ...

Distinctvalues

11- 100

1- 10

101- 1.000

10.001- 100.000

100.001- 1.000.000

4,5067,1729,195

16,607

3,2345,7157,195

16,587

1,0111,0721,4871,536

210333457428

058

21008

Compare number ofdistinct values with totalnumber of records

16,587 combinations ofindex fields return between1 and 10 records


Date/time of analysis: 02.08.1999 17:45:28Analyzed table: COSSTotal number of rows: 635,336 rowsRequested bytes per row: 31 bytes per rowRequested bytes to be buffered 100%: 19,695,416 bytesCurrent buffering mode: no buffering

USPOBKey fields

Rows pergeneric key

GJAHRWRTTP

VERSN

Number of areas that are specified by generic key and contain the given ...

Distinctvalues

11- 100

1- 10

101- 1,000

10,001- 100,000

100,001- 1,000,000

4,5067,1729,195

16,607

3,2345,7157,195

16,587

1,0111,0721,4871,536

210333457428

058

21008

8 combinations of index fields returnbetween 10,001 and 100,000 records

DB05: Selectivity Analysis: Histograms (3)

39


Clarify table usageUse where-used list from ABAP Dictionary

Perform object-related DB SQL cache analysis beforechanging index design

DB SQL cache => restrict to tables and views

Retain all SQL statements with access strategy, where the tablesor views are affected

Change index designReset DB SQL cache

Perform object-related DB SQL cache analysis after changingindex design

DB SQL cache => restrict to tables and views

Retain all SQL statements with access strategy, where the tablesor views are affected

Interference Analysis (1)


Create

Database table VVBAKView

Data type

DomainSearch helpLock object

Display Change

Dictionary object Edit Goto Utilities Environment System HelpDictionary: Initial Screen

DB table VVBAK

Used in

ProgramsScreensLogical databasesFunction module interfaces

DomainsStructuresDB tablesTable typesViewsEntity typesLock objectsSearch helps

Classes (definition)Classes (implementation)Interfaces

Test cases

In background Search area

Where-Used List Database table


40


Database Performance: Shared SQL

??

1999 10:12:21 Shared Cursor Cache

Reset Since DB start Select table Explain

101,002

TotalExecutions

34,0045,340

702

DiskReads

BufferGets

Reads/Executions

Gets/Execution

Records/Execution

4,5067,145

92,195107

0.00.2

17.30.2

45,678109,072

7,041,4871,536

0.53.2

1,318.62.2

0.86.00.41.0

546 16,347 29.9 231,536 424.0

SQLTextSELECT * FROMSELECT “VBELN”SELECT “MANDT”UPDATE“VVBAK”SELECT * FROM47.5

SELECT STATEMENT

TABLE ACESS BY INDEX ROWID VVBAK

INDEX RANGE SCAN VVBAK ~ 0


Database Access OptimizationSuitable Access Path

General Methods

Accessing Individual Tables

Accessing Several Tables

Accessing Clustered and Pooled Tables

R/3 Table Buffering

41


SELECT ... FROM resbINTO TABLE g_itab_resb.

SELECT ... FROM resbINTO TABLE g_itab_resbWHERE matnr IN g_matnr.

Unstable WHERE clauseUnstable WHERE clause

Stable WHERE clauseStable WHERE clause

SELECT ... FROM resbINTO TABLE g_itab_resbWHERE matnr IN g_matnrAND kzear IS INITIAL.

Missing WHERE clauseMissing WHERE clause

Reducing the Records to be Transferred (1)


SELECT vbeln erdat kunnr FROM vvbakINTO g_wa_vvbak.CHECK g_wa_vvbak-vbeln GE g_lowAND g_wa_vvbak-vbeln LE g_high.APPEND g_wa_vvbak TO g_itab_vvbak.

ENDSELECT.

WHERE conditionWHERE condition

SELECT vbeln erdat kunnr FROM vvbakINTO g_wa_vvbakWHERE vbeln BETWEEN g_low AND g_high.APPEND g_wa_vvbak TO g_itab_vvbak.

ENDSELECT.

CHECK

WHERE

CHECK conditionCHECK condition

Reducing the Records to be Transferred (2)

42


Reducing the Columns to be Transferred

SELECT vbeln erdat kunnr FROM vvbakINTO TABLE g_itab_vvbak_fieldlistWHERE vbeln IN g_vbeln.

SELECT * FROM vvbakINTO TABLE g_itab_vvbak_allWHERE vbeln IN g_vbeln.

SET

SELECT

SELECT

SELECT field list INTO TABLESELECT field list INTO TABLE

SELECT vbeln erdat kunnr FROM vvbakINTO CORRESPONDING FIELDSOF TABLE g_itab_vvbak_fieldlistWHERE vbeln IN g_vbeln.

SELECT

SELECT field list INTO ...SELECT field list INTO ...

SELECT * INTO TABLESELECT * INTO TABLE

INTO TABLE

INTO CORRESPONDING FIELDSOF TABLE

INTO TABLE


General Methods




R/3 Table Buffering

43


DESCRIBE TABLE g_itab_vvbak LINES lines.IF lines EQ 0.MESSAGE I051(bc490). EXIT.ENDIF.

SORT g_itab_vvbak BY kunnr.DELETE ADJACENT DUPLICATESFROM g_itab_vvbak.SELECT kunnr adrnr FROM kkna1INTO TABLE g_itab_kkna1FOR ALL ENTRIES IN g_itab_vvbakWHERE kunnr = g_itab_vvbak-kunnr.

LOOP AT g_itab_vvbak INTO g_wa_vvbak.SELECT kunnr adrnr FROM kkna1APPENDING TABLE g_itab_kkna1WHERE kunnr = g_wa_vvbak-kunnr.

ENDLOOP.

LOOP AT

APPENDING TABLE

ENDLOOP.

SELECTINTO TABLEFOR ALL ENTRIES IN

SELECT

SELECT inside LOOPSELECT inside LOOP

SELECT FOR ALL ENTRIESSELECT FOR ALL ENTRIES

Check whether driver table is empty

Eliminate duplicates

SELECT FOR ALL ENTRIES (1)


KKNA1

KKNA1~0

SELECT STATEMENT

CONCATENATION

TABLE ACESS BY INDEX ROWID

INDEX UNIQUE SCAN

TABLE ACESS BY INDEX ROWID KKNA1

KKNA1~0

(Estimated Costs = .... )

Object Oper Rec

FETCH

FETCH

VVBAKVVBAKKKNA1

KKNA1

REOPEN

REOPEN

0100000

FETCHKKNA10

. . .

REOPENKKNA114901490149FETCHKKNA1

REOPENKKNA1

. . . . . .rsdb/max_blocking_factor

specifies numberof concatenations

SELECT"KUNNR" , "ADRNR"

FROM"KKNA1"

WHERE"MANDT" = :A0 AND "KUNNR" = :A1

OR "MANDT" = :A2 AND "KUNNR" = :A3OR "MANDT" = :A4 AND "KUNNR" = :A5OR "MANDT" = :A6 AND "KUNNR" = :A7....

INDEX UNIQUE SCAN

SELECT FOR ALL ENTRIES (2)

44


SELECT mandt vbeln erdat erzetFROM vvbakINTO TABLE g_itab_vvbakWHERE vbeln IN g_itab_vbeln.

SELECT

IN

VVBAK

VVBAK~0

SELECT STATEMENT

CONCATENATION


INDEX UNIQUE SCAN

TABLE ACESS BY INDEX ROWID VVBAK

VVBAK~0


INDEX UNIQUE SCAN

SELECT with RANGES tableSELECT with RANGES tableSELECT

"MANDT" , "VBELN" , "ERDAT" , "ERZET"FROM"VVBAK"

WHERE"MANDT" = :A0AND “VBELN IN ( :A1 , :A2 , :A3 , …)

RANGES Tables


Aggregate functions in ABAPAggregate functions in ABAP

Aggregate functions at DB levelAggregate functions at DB level

SELECT vbeln zmeng matnrFROM vvbapINTO TABLE g_itab_vvbapWHERE vbeln IN g_vbeln.

LOOP AT g_itab_vvbap.* Compute maximum of zmeng and minimum of matnr ...ENDLOOP.

SELECT vbeln max( zmeng ) min( matnr )FROM vvbapINTO TABLE g_itab_vvbapWHERE vbeln IN g_vbelnGROUP BY vbeln.

Aggregate Functions

45


HAVING Clause


Array Fetch

46


Up to N rows


UPDATE .. SET Field = Value

47


Create, Change and Delete Mass Data


General Methods




R/3 Table Buffering

48


INNER and OUTER JOIN Logic

00000000030000000003

INNERJOIN

LEFT OUTERJOIN

MANDT . . .400400

. . . . . .400

MANDT VBELN

0000000001400400

0000000001

. . .. . .400400

MANDT POSNR

0002400

0001

. . .. . .400 0002

0001400

400

VBELN

VBELN

VVBAKVVBAP

00000000010000000001

00000000030000000003

MANDT POSNR

0002400

0001

. . .. . .400 0001400

400

VBELN0000000001

0000000001

00000000020000000003

400 00020000000003. . .. . .

000000000100000000020000000003

POSNR

0000000004400

0001

0002000100020001


Implementation in ABAP

49


Object Oper Rec

FETCH

FETCH

VVBAKVVBAKKKNA1

KKNA1

REOPEN

REOPEN

01000

FETCHKKNA10

. . .

REOPENKKNA110101FETCHKKNA1

REOPENKKNA1

. . . . . .

SELECT STATEMENT

INDEX RANGE SCAN


VVBAK~0

SELECT STATEMENT (Estimated Costs = .... )

KKNA1~0INDEX UNIQUE SCAN

SELECT vbeln kunnr FROM vvbakINTO (g_wa_vvbak_kkna1-vbeln, g_wa_vvbak_kkna1-kunnr)WHERE vbeln IN g_vbeln.SELECT SINGLE adrnr FROM kkna1INTO g_wa_vvbak_kkna1-adrnrWHERE kunnr EQ g_wa_vvbak_kkna1-kunnr.IF sy-subrc EQ 0.APPEND g_wa_vvbak_kkna1 TO g_itab_vvbak_kkna1.

ENDIF.ENDSELECT.

SELECT

SELECT

ENDSELECT

Nested SELECTs


Problems with Nested SELECTs

Inefficient transferData records from inner table are transferred record byrecord

Lots of small fetches, instead of fewer andmore compact fetches

Identical SELECTsData records from inner table arere-read unnecessarily

Incorrect order of accessWhether a table is an inner or outer tableis defined in codingDynamic WHERE conditions are ignored

50


Creating JOINs Over the Database

Possible access strategies:Nested loop

Sort merge join

Database optimizer determines order of accessAccess to outer table should be as selective as possible (selectiveWHERE conditions)

For each data record in the outer table, as few records as possibleshould exist in the inner table (selective JOIN conditions)

An index for the JOIN conditions should existon the inner table (at least)


SELECT vbeln kunnr adrnr FROM vbak_kna1INTO TABLE g_itab_vvbak_kkna1WHERE vbeln IN g_vbeln.

Create DB viewin Dictionary

CREATE VIEWvbak_kna1 ...

SELECT STATEMENT

NESTED LOOPS



KKNA1~0

KKNA1

INDEX UNIQUE SCAN


VVBAK~0

VVBAK

INDEX RANGE SCAN

SELECT FROM vbak_kna1

Database View

51


SELECT t1~vbeln t2~kunnr t2~adrnrINTO TABLE g_itab_vvbak_kkna1FROM vvbak AS t1INNER JOIN kkna1 AS t2ON t1~kunnr = t2~kunnrWHERE t1~vbeln IN g_vbeln.

SELECT STATEMENT

NESTED LOOPS



KKNA1~0

KKNA1

INDEX UNIQUE SCAN


VVBAK~0

VVBAK

INDEX RANGE SCAN

MANDT VBELN KUNNR...

001 0000120 0000100001 0000121 0000100001 0000122 0000101001 0000123 0000101001 0000124 0000102001 0000125 0000103001 0000126 0000103001 0000127 0000104

...

VVBAK

KKNA1

MANDT KUNNR ...001 0000100 ...001 0000103 ...001 0000104 ......

SELECT

INNER JOIN ASAS

ON

ABAP INNER JOIN


SELECT STATEMENT

CONCATENATION


TABLE ACCESS BY INDEX ROWID

KKNA1~0

KKNA1

INDEX UNIQUE SCAN


KKNA1~0

KKNA1

INDEX UNIQUE SCAN

SELECT vbeln kunnr FROM vvbak INTO TABLE g_itab_vvbakWHERE vbeln IN g_vbeln.

DESCRIBE TABLE g_itab_vvbakLINES g_lines....

SORT g_itab_kkna1 BY kunnr.DELETE ADJACENT DUPLICATESFROM g_itab_kkna1.

SELECT kunnr adrnrFROM kkna1INTO (g_wa_kkna1-kunnr, g_wa_kkna1-adrnr)FOR ALL ENTRIES IN g_itab_kkna1WHERE kunnr = g_itab_kkna1-kunnr.

MODIFY g_itab_kkna1 FROM g_wa_kkna1 INDEX sy-dbcnt.ENDSELECT.

LOOP AT g_itab_vvbak INTO g_wa_vvbak....

ENDLOOP.

FOR ALL ENTRIES IN

SELECT

SELECT

DESCRIBE TABLE

DELETE ADJACENT DUPLICATES

FOR ALL ENTRIES Over Two Database Tables

52


...SELECT kunnr adrnrINTO TABLE g_itab_vvbak_kkna1FROM kkna1WHERE kunnr IN ( SELECT DISTINCT kunnr FROM vvbak

WHERE vbeln IN g_vbeln )....

...

VVBAK~0

KKNA1~0INDEX UNIQUE SCAN


NESTED LOOPS

SELECT STATEMENT

…



INDEX RANGE SCAN

VVBAK

KKNA1

)(WHERE

SELECT

SELECT DISTINCT

Subquery


SELECT STATEMENT


VVBAK~0INDEX RANGE SCAN



INDEX UNIQUE SCAN KKNA1~0

VVBAK

NESTED LOOPS OUTER

KKNA1

SELECT t1~vbeln t2~kunnr t2~adrnrINTO TABLE g_itab_vvbak_kkna1FROM vvbak AS t1LEFT OUTER JOIN kkna1 AS t2ON t1~kunnr = t2~kunnrWHERE t1~vbeln IN g_vbeln.

SELECT

LEFT OUTER JOIN ASAS

ON

MANDT VBELN KUNNR...

001 0000120 0000100001 0000121 0000100001 0000122 0000101001 0000123 0000101001 0000124 0000102001 0000125 0000103001 0000126 0000103001 0000127 0000104

...

VVBAK

KKNA1

MANDT KUNNR ...001 0000100 ...001 0000103 ...001 0000104 ......

ABAP OUTER JOIN

53


General Methods




R/3 Table Buffering


Logical view

Physical view

TAB_B

Transparent tables Cluster tables Pooled tables

POOL_ACLUST_APOOL_B

Database tables

CLUST_BCLUST_C

Pooled and Cluster Tables: Introduction

54


A C DB

A E FB

A H IB

A B

A B

0

1

PAGNO

TIMESTAMP PAGELG

C D E

G H I

Cluster table TABA

Cluster table TABB

Table clusterTABAB

Key fields

Key fields

G

J

F

J

VARDATA fieldClusterkey

Structure descriptionof VARDATA field

Cluster Tables


A CB

E G

E

BTABA

TABB

DATALN

C D

F G

Pooled table TABA

Pooled table TABB

Table poolTABAB

Key

Key

I

H

VARDATAVARKEY

D

H

A

F

I

TABNAME

Pooled Tables

55


Advantages Disadvantages

Data compressionLess memory space

Less network load

Fewer tables and table fields

Fewer different SQLstatements

Less load on databasedictionary and databasebuffer

Simpler administration

For cluster tablesFewer database accesses

Limitations on databasefunctionalities

No views or ABAP JOINs

No secondary indexes

No GROUP BY, ORDER BY, ...

No native SQL

No table appends

For cluster tablesLimited selection on clusterkeyfields

For pooled tablesLonger keys than necessary

Pooled and Cluster Tables: Pros and Cons


SELECT bukrs belnr gjahr kunnrFROM bsegINTO TABLE g_itab_bsidWHERE bukrs = ‘0001’AND belnr = ‘0000000022’.

SELECT “MANDT”, “BUKRS”, “BELNR”, “GJAHR”, “PAGENO”,“TIMESTMP”, “PAGELG”, “VARDATA”FROM “RFBLG”WHERE “MANDT” = :A0AND “BUKRS” = :A1AND “BELNR” = :A2

ORDER BY “MANDT”, “BUKRS”, “BELNR”, “GJAHR”, “PAGENO”

SQL statement at DB levelSQL statement at DB level

RFBLG

bseg

SQL statement in ABAPSQL statement in ABAP

Selective Access to Cluster Tables

56


SELECT bukrs belnr ...FROM bsegINTO TABLE g_itab_bsidWHERE kunnr = '0000000100'.

SELECT bukrs belnr …FROM bsidINTO TABLE g_itab_bsidWHERE kunnr = '0000000100'.

SELECT “BUKRS”, “MANDT”, ..FROM BSIDWHERE “MANDT” = :A0AND “KUNNR” = :A1.

Selective accessSelective access

SELECT “MANDT”, “BUKRS”, ..FROM “RFBLG”WHERE “MANDT” = :A0ORDER BY “MANDT”, “BUKRS”,...

KUNNR

BSID

RFBLG

bsid

kunnr

bseg

kunnr

Unselective accessUnselective access

Unselective Access on Cluster Tables


SELECT kappl kschl vkorg vtweg matnr FROM aa005INTO TABLE g_itab_aa005WHERE kappl = ‘CS’ AND kschl = ‘SAPZ’AND vkorg = ‘0001’ AND vtweg = ‘01’AND kunnr = ‘0000000009’AND matnr = ‘000000000000000027’.

SELECT“TABNAME” , “VARKEY” , “DATALN” , “VARDATA”FROM“KAPOL”WHERE“TABNAME” = :A0 AND “VARKEY” LIKE :A1ORDER BY “TABNAME” , “VARKEY”

SQL statement at DB levelSQL statement at DB level

TABNAME VARKEY

KAPOL

aa005

SQL statement in ABAPSQL statement in ABAP

Selective Access on Pooled Tables

57


SELECT kappl kschl vkorg ..FROM aa005INTO TABLE g_itab_aa005WHERE matnr =

‘000000000000000027’.

AA005 fully bufferedon application server

<=>Repeated database read

is not necessary

Selective accessSelective access

SELECT “TABNAME”, “VARKEY” ..FROM “KAPOL”WHERE “TABNAME” = :A0 AND“VARKEY” LIKE :A1ORDER BY “TABNAME” , ..

Remove AA05 from table pool KAPOLand create index for MATNR

<=>Efficient data read

is possible

aa005

matnr

KAPOLTABNAME

VARKEY

Unselective accessUnselective access

Unselective Access on Pooled Tables


General Methods




R/3 Table Buffering

58


Application server A

SAP GUI SAP GUI

...

...

R/3 buffer

Network

DatabaseManagementSystem

DBMSprocesses

Databasebuffer

Database

Application server B

SAP GUI SAP GUI

...

...

Program bufferDictionary bufferNumber range bufferRoll and paging buffers

Table buffer

R/3 buffer...

R/3 Table Buffering: Introduction (1)



Table buffer

Network

DBMS DBMSprocesses

Databasebuffer

Database

SELECT * FROM VVBAKWHERE ...

Database interface

ABAP program

8 - 600 ms

0.2 - 6 ms

R/3 Table Buffering: Introduction (2)

59


key1 key2 key3 data

key1 key2 key3 data

key1 key2 key3 data

key1 key2 key3 data

Full buffering(100%)

Generic bufferingwith 1 key field

Generic bufferingwith 2 key fields

Single-record buffering

001001001001002002002002002002003003003003003003003003

001001001001002002002002002002002002003003003003003003003003003003003

001001001001001002002002002002002002002002002003003003003003003003003003003003003003

AA

BB

AABBBC

DC

AAABBCCCDDD

AA

BB

BAAAABBBC

DC

AAABBCCCCDDDD

42

31

513681230

53

2362423581234

Types of Buffering


DB interface


Table buffer

Network

Database management system

Database

Application server B

Table buffer...

DDLOG

Buffer synchronizationevery 1 - 2 minutes

UPDATE TCURR...

DB interface

INSERT DDLOG SELECT DDLOG

DB interface

1

2

3

Buffer Synchronization

60


In work area mode (single record processing)

Full buffering: All records

Generic buffering: Generic area

Single record buffering: Changed single record

In set mode (mass processing)

All records regardless of type of buffering

Degree of Invalidation


Native SQL

Subqueries, ABAP JOINs)

SELECT ... BYPASSING BUFFER

SELECT FOR UPDATE

Aggregate functions (COUNT, MIN, MAX, SUM, AVG)

SELECT DISTINCT …

WHERE clause with "IS NULL"

ORDER BY, GROUP BY (HAVING)

For tables with single record buffering:All SQL statements except SELECT SINGLE ...

For tables with generic buffering:All SQL statements except SELECT * .. if WHERE clause isfield = value for all fields included in generic area

SQL Statements that Bypass the Buffer (1)

61


SQL Statements that Bypass the Buffer (2)

SELECT * FROM tcurrCLIENT SPECIFIEDINTO TABLE g_itab_tcurrWHERE kurst = 'EURO'.

SELECT * FROM t100INTO TABLE g_itab_t100WHERE sprsl = 'D'AND arbgb = 'BC490'AND msgnr = '050'.

Generic bufferingGeneric buffering

Single record bufferingSingle record buffering

SELECT * FROM tcurrINTO TABLE g_itab_tcurrWHERE kurst = 'EURO'.

SELECT SINGLE * FROM t100INTO g_wa_t100WHERE sprsl = 'D'AND arbgb = 'BC490'AND msgnr = '050'.

CLIENT SPECIFIED

=> Database =>Table buffer

=> Database =>Table bufferSINGLE


Technical criteriaSmall, usually < 1 MBOften read, but seldom changedTemporary data inconsistency acceptableAccess mainly from key fields

Note:Buffer tables > 10 MB in exceptional cases onlyTable buffers cannot be accessed via secondary indexesCheck available memory space before buffering more tables

Buffering Strategy: Technical Criteria

62


Buffering Strategy: Semantic Criteria

Do not buffer transaction dataTables too bigTables changed frequently

Avoid buffering master dataTables too bigDifferent access paths to data

Buffer Customizing dataTables smallFew changes to tables

Internal Table OptimizationDefinition and Properties

Efficient composition of internal tables

Efficient access to internal tables

63


Internal Table Attributes


Key access

Access costs increase linearly increase logarithmically are constantfor n entries O(n) O(log n) O(1)

Access using

mainly index mainly key only key

Uniqueness NON-UNIQUE UNIQUE | NON-UNIQUE UNIQUE

STANDARD TABLE SORTED TABLE

INDEX TABLE HASHED TABLE

ANY TABLE

nn

Table scan Binary search Hashfunction

Table Types

64


Defining Internal Tables


Reading Single Records

65


Loop costsdepending onthe internaltable type

10

100

1000

1000

01E

+051E

+06

5 10 20 40 80 160 320 640 1280

Number of table entries in both tables: n

Tim

e in

mic

rose

cond

s

Standard 52 121 335 1081 3887 14999 59700 238214 951704Sorted 44 87 177 391 862 1895 4048 8587 18136Hashed 41 78 151 305 613 1249 2497 5080 10537

5 10 20 40 80 160 320 640 1280

LOOP AT outer_tab INTO wa_out.READ TABLE inner_tab INTO wa_in WITH TABLE KEY ...

ENDLOOP.

LOOPREAD TABLE WITH TABLE KEY

Access Costs: Single Record Access via Key


Hashed Tables

LOOP AT sort_vbap INTO wa_vbap.

AT NEW wa_vbap-vbeln.READ TABLE hash_vbak INTO wa_vbak WITH TABLE KEY

mandt = sy-mandt vbeln = wa_vbap-vbeln.WRITE: / wa_vbak-vbeln, wa_vbak-erdat.

ENDAT.

WRITE: /10 wa_vbap-posnr, ... .ENDLOOP.

Single record access with full specification of the primary key

MANDT VBELN ...MANDT VBELN ...

hash_vbak:

READ TABLE

LOOP

66


LOOP AT sort_vbpa INTO wa_vbpaWHERE mandt = sy-mandt

AND parvw = 'WE'.ENDLOOP.

Mass processing with partial specification of the key- Try to include as many key fields in the WHERE condition aspossible; starting from the left key field, and without skipping a keyfield.

MANDT VBELN POSNR PARVWMANDT VBELN POSNR PARVW

sort_vbpa:LOOP ... WHEREDELETE ... WHEREMODIFY ... WHERE

Sorted Tables

LOOP AT sort_vbpa INTO wa_vbpaWHERE mandt = sy-mandt

AND vbeln = '0000000900'.ENDLOOP.

DELETE TABLE sort_vbpaWHERE mandt = sy-mandt

AND vbeln = '0000000900'.

LOOPWHERE

DELETE TABLEWHERE


Standard Tables

PARAMETERS: p_ernam TYPE vbak-ernam,p_vdatu TYPE vbak-vdatu.

SORT stan_vbak BY ernam.READ TABLE stan_vbak WITH KEY ernam = p_ernam INTO wa

BINARY SEARCH.IF sy-subrc NE 0. ... ENDIF.

SORT stan_vbak BY erdat vdatu.LOOP AT stan_vbak INTO wa WHERE erdat = sy-datu

AND vdatu = p_vdatu.IF wa-erdat NE sy-datu OR wa-vdatu NE p_vdatu.

EXIT.ENDIF.

ENDLOOP.

Flexible accessfor example, using various keys

SORT BYREAD

SORTLOOP

BY

67





Array Fetch

68


Inserting Internal Tables


Filling an Internal Table with Cumulative Values

69


Loading Unique Internal Tables




70


Limited Mass Data Access


Selective Field Transport

71


Using Field Symbols


Access on Tables without Field Transfer

72


Reading Single Records

Use BINARY SEARCHfor standard tables(after sorting)

READ TABLE ... BINARY SEARCH.

READ TABLE ... ...INDEX

READ TABLE ... FROM <WA>.READ TABLE ... WITH TABLE KEY ...

FROMWITH TABLE KEY ...

If you can fully specifythe primary key, useFROM or WITH TABLE KEY

If possible, use indexoperations (not possiblewith hashed tables)


i_vbak

wa

mandt vbeln

400 0000000110

400400400400400

Reading Single Records: Example

READ TABLE i_vbak WITH KEYmandt = sy-mandtvbeln = ‘0000000110‘ INTO wa.

wa-mandt = sy-mandt.wa-vbeln = ‘0000000110'.READ TABLE i_vbak FROM wa INTO wa.

* or

READ TABLE i_vbak WITH TABLE KEYmandt = sy-mandtvbeln = ‘0000000110‘ INTO wa.

* for standard tables:

SORT i_vbak BY mandt vbeln.READ TABLE i_vbak INTO wa

mandt = sy-mandtvbeln = ‘0000000110‘

BINARY SEARCH .

00000001000000000110000000012000000001300000001000

WA

i_vbak

WITH KEY

READ FROM

READ WITH TABLE KEY

READWITH KEY

BINARY SEARCH

73


Mass Processing using a WHERE Clause

SELECT-OPTIONS:s_vbeln FOR vbak-vbeln.

LOOP AT stan_vbap INTO wa.IF wa-vbeln IN s_vbeln.

* ...ENDIF.

ENDLOOP.

LOOP AT <itab> ... WHERE ...MODIFY <itab> ... WHERE ...DELETE <itab> ... WHERE ...

Only access the table lines you really need

SELECT-OPTIONS:s_vbeln FOR vbak-vbeln.

LOOP AT stan_vbap INTO waWHERE mandt = sy-mandt

AND vbeln IN s_vbeln.ENDLOOP.

LOOP ATMODIFYDELETE WHERE

LOOP LOOPWHERE

WHEREWHERE


Mass Processing using an Index Interval

LOOP AT sort_vbakASSIGNING <fs_vbak>.

LOOP AT sort_vbap ...WHERE VBELN = <fs_vbak>-vbeln.

ENDLOOP.

ENDLOOP.

LOOP ... FROM ... TO ... .APPEND ... FROM ... TO ... .INSERT ... FROM ... TO ... .DELETE ... FROM ... TO ... .

index = 1.LOOP AT sort_vbak

ASSIGNING <fs_vbak>.LOOP AT sort_vbap

ASSIGNING <fs_vbap>FROM index.

IF <fs_vbap>-vbeln NE<fs_vbak>-vbeln.

index = sy-tabix.EXIT.

ENDIF.ENDLOOP.

ENDLOOP.

2

12345

1234..10

1

Sort_vbak Sort_vbakindexOnly access the table lines you

really need1

2

3...

FROM index.

index

FROMFROMFROMFROM

TOTOTOTO

Documents

SPOW (Performance Optimization Workshop)