Performance Tunning

Former Member · ‎11-22-2007

Does using

CLEAR

REFRESH

FREE for internal tables reduce the performance of the program??

What are all the steps taken to improve the performance of the program.

Former Member · ‎11-22-2007

work area used used clear wa.

with header line refresh are free.

without headerline use clear work area. best ne to ues program.

ecc 6.0 allwed only wa.

Former Member · ‎11-22-2007

clear, refresh will not reduce pperformance

Free will improve the memory usage part , if u free memory for tables that u are not going to use after some part

.

Former Member · ‎11-22-2007

nope these will not decrease the performance of the programs...............

Follow the steps mentioned for better performance:

1) Don’t use nested select statement

2) If possible use for all entries in addition

3) In the where addition make sure you give all the primary key

4) Use Index for the selection criteria.

5) You can also use inner joins

6) You can try to put the data from the first select statement into an Itab and then in order to select the data from the second table use for all entries in.

7) do avoid nested loops

😎 whenever you use READ statement WITH KEY do BINARY SEARCH.

9) when you have large tables with a unique index use hash tables

10) avoid using the progress_bar fm

11) do avoid SQL-Statements inside loops - rather modify internal table and at the end modify dbtab from itab where applicable.

12) Unused/Dead code

Avoid leaving unused code in the program. Either comment out or delete the unused situation. Use program --> check --> extended program to check for the variables, which are not used statically.

13) Subroutine Usage

For good modularization, the decision of whether or not to execute a subroutine should be made before the subroutine is called. For example:

This is better:

IF f1 NE 0.

PERFORM sub1.

ENDIF.

FORM sub1.

...

ENDFORM.

Than this:

PERFORM sub1.

FORM sub1.

IF f1 NE 0.

...

ENDIF.

ENDFORM.

14)Usage of IF statements

When coding IF tests, nest the testing conditions so that the outer conditions are those which are most likely to fail. For logical expressions with AND , place the mostly likely false first and for the OR, place the mostly likely true first.

Example - nested IF's:

IF (least likely to be true).

IF (less likely to be true).

IF (most likely to be true).

ENDIF.

Example - IF...ELSEIF...ENDIF :

IF (most likely to be true).

ELSEIF (less likely to be true).

ELSEIF (least likely to be true).

ENDIF.

Example - AND:

IF (least likely to be true) AND

(most likely to be true).

ENDIF.

Example - OR:

IF (most likely to be true) OR

(least likely to be true).

15)CASE vs. nested Ifs

When testing fields "equal to" something, one can use either the nested IF or the CASE statement. The CASE is better for two reasons. It is easier to read and after about five nested IFs the performance of the CASE is more efficient.

16)MOVE statements

When records a and b have the exact same structure, it is more efficient to MOVE a TO b than to MOVE-CORRESPONDING a TO b.

MOVE BSEG TO *BSEG.

is better than

MOVE-CORRESPONDING BSEG TO *BSEG.

17)SELECT and SELECT SINGLE

When using the SELECT statement, study the key and always provide as much of the left-most part of the key as possible. If the entire key can be qualified, code a SELECT SINGLE not just a SELECT. If you are only interested in the first row or there is only one row to be returned, using SELECT SINGLE can increase performance by up to three times.

18)Small internal tables vs. complete internal tables

In general it is better to minimize the number of fields declared in an internal table. While it may be convenient to declare an internal table using the LIKE command, in most cases, programs will not use all fields in the SAP standard table.

For example:

Instead of this:

data: t_mara like mara occurs 0 with header line.

Use this:

data: begin of t_mara occurs 0,

matnr like mara-matnr,

...

end of t_mara.

19)Row-level processing and SELECT SINGLE

Similar to the processing of a SELECT-ENDSELECT loop, when calling multiple SELECT-SINGLE commands on a non-buffered table (check Data Dictionary -> Technical Info), you should do the following to improve performance:

o Use the SELECT into <itab> to buffer the necessary rows in an internal table, then

o sort the rows by the key fields, then

o use a READ TABLE WITH KEY ... BINARY SEARCH in place of the SELECT SINGLE command. Note that this only make sense when the table you are buffering is not too large (this decision must be made on a case by case basis).

20)READing single records of internal tables

When reading a single record in an internal table, the READ TABLE WITH KEY is not a direct READ. This means that if the data is not sorted according to the key, the system must sequentially read the table. Therefore, you should:

o SORT the table

o use READ TABLE WITH KEY BINARY SEARCH for better performance.

21)SORTing internal tables

When SORTing internal tables, specify the fields to SORTed.

SORT ITAB BY FLD1 FLD2.

is more efficient than

SORT ITAB.

22)Number of entries in an internal table

To find out how many entries are in an internal table use DESCRIBE.

DESCRIBE TABLE ITAB LINES CNTLNS.

is more efficient than

LOOP AT ITAB.

CNTLNS = CNTLNS + 1.

ENDLOOP.

23)Performance diagnosis

To diagnose performance problems, it is recommended to use the SAP transaction SE30, ABAP/4 Runtime Analysis. The utility allows statistical analysis of transactions and programs.

24)Nested SELECTs versus table views

Since releASE 4.0, OPEN SQL allows both inner and outer table joins. A nested SELECT loop may be used to accomplish the same concept. However, the performance of nested SELECT loops is very poor in comparison to a join. Hence, to improve performance by a factor of 25x and reduce network load, you should either create a view in the data dictionary then use this view to select data, or code the select using a join.

25)If nested SELECTs must be used

As mentioned previously, performance can be dramatically improved by using views instead of nested SELECTs, however, if this is not possible, then the following example of using an internal table in a nested SELECT can also improve performance by a factor of 5x:

Use this:

form select_good.

data: t_vbak like vbak occurs 0 with header line.

data: t_vbap like vbap occurs 0 with header line.

select * from vbak into table t_vbak up to 200 rows.

select * from vbap

for all entries in t_vbak

where vbeln = t_vbak-vbeln.

...

endselect.

endform.

Instead of this:

form select_bad.

select * from vbak up to 200 rows.

select * from vbap where vbeln = vbak-vbeln.

...

endselect.

endform.

Although using "SELECT...FOR ALL ENTRIES IN..." is generally very fast, you should be aware of the three pitfalls of using it:

Firstly, SAP automatically removes any duplicates from the rest of the retrieved records. Therefore, if you wish to ensure that no qualifying records are discarded, the field list of the inner SELECT must be designed to ensure the retrieved records will contain no duplicates (normally, this would mean including in the list of retrieved fields all of those fields that comprise that table's primary key).

Secondly, if you were able to code "SELECT ... FROM <database table> FOR ALL ENTRIES IN TABLE <itab>" and the internal table <itab> is empty, then all rows from <database table> will be retrieved.

Thirdly, if the internal table supplying the selection criteria (i.e. internal table <itab> in the example "...FOR ALL ENTRIES IN TABLE <itab> ") contains a large number of entries, performance degradation may occur.

26)SELECT * versus SELECTing individual fields

In general, use a SELECT statement specifying a list of fields instead of a SELECT * to reduce network traffic and improve performance. For tables with only a few fields the improvements may be minor, but many SAP tables contain more than 50 fields when the program needs only a few. In the latter case, the performace gains can be substantial. For example:

Use:

select vbeln auart vbtyp from table vbak

into (vbak-vbeln, vbak-auart, vbak-vbtyp)

where ...

Instead of using:

select * from vbak where ...

27)Avoid unnecessary statements

There are a few cases where one command is better than two. For example:

Use:

append <tab_wa> to <tab>.

Instead of:

<tab> = <tab_wa>.

append <tab> (modify <tab>).

And also, use:

if not <tab>[] is initial.

Instead of:

describe table <tab> lines <line_counter>.

if <line_counter> > 0.

28)Copying or appending internal tables

Use this:

<tab2>[] = <tab1>[]. (if <tab2> is empty)

Instead of this:

loop at <tab1>.

append <tab1> to <tab2>.

endloop.

However, if <tab2> is not empty and should not be overwritten, then use:

append lines of <tab1> [from index1] [to index2] to <tab2>.

Former Member · ‎11-22-2007

hi

these are the points to take

Ways of Performance Tuning

1. Selection Criteria

2. Select Statements

• Select Queries

• SQL Interface

• Aggregate Functions

• For all Entries

Select Over more than one Internal table

Selection Criteria

1. Restrict the data to the selection criteria itself, rather than filtering it out using the ABAP code using CHECK statement.

2. Select with selection list.

Points # 1/2

SELECT * FROM SBOOK INTO SBOOK_WA.

CHECK: SBOOK_WA-CARRID = 'LH' AND

SBOOK_WA-CONNID = '0400'.

ENDSELECT.

The above code can be much more optimized by the code written below which avoids CHECK, selects with selection list

SELECT CARRID CONNID FLDATE BOOKID FROM SBOOK INTO TABLE T_SBOOK

WHERE SBOOK_WA-CARRID = 'LH' AND

SBOOK_WA-CONNID = '0400'.

Select Statements Select Queries

1. Avoid nested selects

2. Select all the records in a single shot using into table clause of select statement rather than to use Append statements.

3. When a base table has multiple indices, the where clause should be in the order of the index, either a primary or a secondary index.

4. For testing existence , use Select.. Up to 1 rows statement instead of a Select-Endselect-loop with an Exit.

5. Use Select Single if all primary key fields are supplied in the Where condition .

Point # 1

SELECT * FROM EKKO INTO EKKO_WA.

SELECT * FROM EKAN INTO EKAN_WA

WHERE EBELN = EKKO_WA-EBELN.

ENDSELECT.

The above code can be much more optimized by the code written below.

SELECT P_{F1 P}F2 F_{F3 F}F4 INTO TABLE ITAB

FROM EKKO AS P INNER JOIN EKAN AS F

ON P_{EBELN = F}EBELN.

Note: A simple SELECT loop is a single database access whose result is passed to the ABAP program line by line. Nested SELECT loops mean that the number of accesses in the inner loop is multiplied by the number of accesses in the outer loop. One should therefore use nested SELECT loops only if the selection in the outer loop contains very few lines or the outer loop is a SELECT SINGLE statement.

Point # 2

SELECT * FROM SBOOK INTO SBOOK_WA.

CHECK: SBOOK_WA-CARRID = 'LH' AND

SBOOK_WA-CONNID = '0400'.

ENDSELECT.

The above code can be much more optimized by the code written below which avoids CHECK, selects with selection list and puts the data in one shot using into table

SELECT CARRID CONNID FLDATE BOOKID FROM SBOOK INTO TABLE T_SBOOK

WHERE SBOOK_WA-CARRID = 'LH' AND

SBOOK_WA-CONNID = '0400'.

Point # 3

To choose an index, the optimizer checks the field names specified in the where clause and then uses an index that has the same order of the fields . In certain scenarios, it is advisable to check whether a new index can speed up the performance of a program. This will come handy in programs that access data from the finance tables.

Point # 4

SELECT * FROM SBOOK INTO SBOOK_WA

UP TO 1 ROWS

WHERE CARRID = 'LH'.

ENDSELECT.

The above code is more optimized as compared to the code mentioned below for testing existence of a record.

SELECT * FROM SBOOK INTO SBOOK_WA

WHERE CARRID = 'LH'.

EXIT.

ENDSELECT.

Point # 5

If all primary key fields are supplied in the Where condition you can even use Select Single.

Select Single requires one communication with the database system, whereas Select-Endselect needs two.

Select Statements contd.. SQL Interface

1. Use column updates instead of single-row updates

to update your database tables.

2. For all frequently used Select statements, try to use an index.

3. Using buffered tables improves the performance considerably.

Point # 1

SELECT * FROM SFLIGHT INTO SFLIGHT_WA.

SFLIGHT_WA-SEATSOCC =

SFLIGHT_WA-SEATSOCC - 1.

UPDATE SFLIGHT FROM SFLIGHT_WA.

ENDSELECT.

The above mentioned code can be more optimized by using the following code

UPDATE SFLIGHT

SET SEATSOCC = SEATSOCC - 1.

Point # 2

SELECT * FROM SBOOK CLIENT SPECIFIED INTO SBOOK_WA

WHERE CARRID = 'LH'

AND CONNID = '0400'.

ENDSELECT.

The above mentioned code can be more optimized by using the following code

SELECT * FROM SBOOK CLIENT SPECIFIED INTO SBOOK_WA

WHERE MANDT IN ( SELECT MANDT FROM T000 )

AND CARRID = 'LH'

AND CONNID = '0400'.

ENDSELECT.

Point # 3

Bypassing the buffer increases the network considerably

SELECT SINGLE * FROM T100 INTO T100_WA

BYPASSING BUFFER

WHERE SPRSL = 'D'

AND ARBGB = '00'

AND MSGNR = '999'.

The above mentioned code can be more optimized by using the following code

SELECT SINGLE * FROM T100 INTO T100_WA

WHERE SPRSL = 'D'

AND ARBGB = '00'

AND MSGNR = '999'.

Select Statements contd… Aggregate Functions

• If you want to find the maximum, minimum, sum and average value or the count of a database column, use a select list with aggregate functions instead of computing the aggregates yourself.

Some of the Aggregate functions allowed in SAP are MAX, MIN, AVG, SUM, COUNT, COUNT( * )

Consider the following extract.

Maxno = 0.

Select * from zflight where airln = ‘LF’ and cntry = ‘IN’.

Check zflight-fligh > maxno.

Maxno = zflight-fligh.

Endselect.

The above mentioned code can be much more optimized by using the following code.

Select max( fligh ) from zflight into maxno where airln = ‘LF’ and cntry = ‘IN’.

Select Statements contd…For All Entries

• The for all entries creates a where clause, where all the entries in the driver table are combined with OR. If the number of entries in the driver table is larger than rsdb/max_blocking_factor, several similar SQL statements are executed to limit the length of the WHERE clause.

The plus

• Large amount of data

• Mixing processing and reading of data

• Fast internal reprocessing of data

• Fast

The Minus

• Difficult to program/understand

• Memory could be critical (use FREE or PACKAGE size)

Points to be must considered FOR ALL ENTRIES

• Check that data is present in the driver table

• Sorting the driver table

• Removing duplicates from the driver table

Consider the following piece of extract

Loop at int_cntry.

Select single * from zfligh into int_fligh

where cntry = int_cntry-cntry.

Append int_fligh.

Endloop.

The above mentioned can be more optimized by using the following code.

Sort int_cntry by cntry.

Delete adjacent duplicates from int_cntry.

If NOT int_cntry[] is INITIAL.

Select * from zfligh appending table int_fligh

For all entries in int_cntry

Where cntry = int_cntry-cntry.

Endif.

Select Statements contd… Select Over more than one Internal table

1. Its better to use a views instead of nested Select statements.

2. To read data from several logically connected tables use a join instead of nested Select statements. Joins are preferred only if all the primary key are available in WHERE clause for the tables that are joined. If the primary keys are not provided in join the Joining of tables itself takes time.

3. Instead of using nested Select loops it is often better to use subqueries.

Point # 1

SELECT * FROM DD01L INTO DD01L_WA

WHERE DOMNAME LIKE 'CHAR%'

AND AS4LOCAL = 'A'.

SELECT SINGLE * FROM DD01T INTO DD01T_WA

WHERE DOMNAME = DD01L_WA-DOMNAME

AND AS4LOCAL = 'A'

AND AS4VERS = DD01L_WA-AS4VERS

AND DDLANGUAGE = SY-LANGU.

ENDSELECT.

The above code can be more optimized by extracting all the data from view DD01V_WA

SELECT * FROM DD01V INTO DD01V_WA

WHERE DOMNAME LIKE 'CHAR%'

AND DDLANGUAGE = SY-LANGU.

ENDSELECT

Point # 2

SELECT * FROM EKKO INTO EKKO_WA.

SELECT * FROM EKAN INTO EKAN_WA

WHERE EBELN = EKKO_WA-EBELN.

ENDSELECT.

The above code can be much more optimized by the code written below.

SELECT P_{F1 P}F2 F_{F3 F}F4 INTO TABLE ITAB

FROM EKKO AS P INNER JOIN EKAN AS F

ON P_{EBELN = F}EBELN.

Point # 3

SELECT * FROM SPFLI

INTO TABLE T_SPFLI

WHERE CITYFROM = 'FRANKFURT'

AND CITYTO = 'NEW YORK'.

SELECT * FROM SFLIGHT AS F

INTO SFLIGHT_WA

FOR ALL ENTRIES IN T_SPFLI

WHERE SEATSOCC < F~SEATSMAX

AND CARRID = T_SPFLI-CARRID

AND CONNID = T_SPFLI-CONNID

AND FLDATE BETWEEN '19990101' AND '19990331'.

ENDSELECT.

The above mentioned code can be even more optimized by using subqueries instead of for all entries.

SELECT * FROM SFLIGHT AS F INTO SFLIGHT_WA

WHERE SEATSOCC < F~SEATSMAX

AND EXISTS ( SELECT * FROM SPFLI

WHERE CARRID = F~CARRID

AND CONNID = F~CONNID

AND CITYFROM = 'FRANKFURT'

AND CITYTO = 'NEW YORK' )

AND FLDATE BETWEEN '19990101' AND '19990331'.

ENDSELECT.

1. Table operations should be done using explicit work areas rather than via header lines.

2. Always try to use binary search instead of linear search. But don’t forget to sort your internal table before that.

3. A dynamic key access is slower than a static one, since the key specification must be evaluated at runtime.

4. A binary search using secondary index takes considerably less time.

5. LOOP ... WHERE is faster than LOOP/CHECK because LOOP ... WHERE evaluates the specified condition internally.

6. Modifying selected components using “ MODIFY itab …TRANSPORTING f1 f2.. “ accelerates the task of updating a line of an internal table.

Point # 2

READ TABLE ITAB INTO WA WITH KEY K = 'X‘ BINARY SEARCH.

IS MUCH FASTER THAN USING

READ TABLE ITAB INTO WA WITH KEY K = 'X'.

If TAB has n entries, linear search runs in O( n ) time, whereas binary search takes only O( log2( n ) ).

Point # 3

READ TABLE ITAB INTO WA WITH KEY K = 'X'. IS FASTER THAN USING

READ TABLE ITAB INTO WA WITH KEY (NAME) = 'X'.

Point # 5

LOOP AT ITAB INTO WA WHERE K = 'X'.

" ...

ENDLOOP.

The above code is much faster than using

LOOP AT ITAB INTO WA.

CHECK WA-K = 'X'.

" ...

ENDLOOP.

Point # 6

WA-DATE = SY-DATUM.

MODIFY ITAB FROM WA INDEX 1 TRANSPORTING DATE.

The above code is more optimized as compared to

WA-DATE = SY-DATUM.

MODIFY ITAB FROM WA INDEX 1.

7. Accessing the table entries directly in a "LOOP ... ASSIGNING ..." accelerates the task of updating a set of lines of an internal table considerably

8. If collect semantics is required, it is always better to use to COLLECT rather than READ BINARY and then ADD.

9. "APPEND LINES OF itab1 TO itab2" accelerates the task of appending a table to another table considerably as compared to “ LOOP-APPEND-ENDLOOP.”

10. “DELETE ADJACENT DUPLICATES“ accelerates the task of deleting duplicate entries considerably as compared to “ READ-LOOP-DELETE-ENDLOOP”.

11. "DELETE itab FROM ... TO ..." accelerates the task of deleting a sequence of lines considerably as compared to “ DO -DELETE-ENDDO”.

Point # 7

Modifying selected components only makes the program faster as compared to Modifying all lines completely.

e.g,

LOOP AT ITAB ASSIGNING <WA>.

I = SY-TABIX MOD 2.

IF I = 0.

<WA>-FLAG = 'X'.

ENDIF.

ENDLOOP.

The above code works faster as compared to

LOOP AT ITAB INTO WA.

I = SY-TABIX MOD 2.

IF I = 0.

WA-FLAG = 'X'.

MODIFY ITAB FROM WA.

ENDIF.

ENDLOOP.

Point # 8

LOOP AT ITAB1 INTO WA1.

READ TABLE ITAB2 INTO WA2 WITH KEY K = WA1-K BINARY SEARCH.

IF SY-SUBRC = 0.

ADD: WA1-VAL1 TO WA2-VAL1,

WA1-VAL2 TO WA2-VAL2.

MODIFY ITAB2 FROM WA2 INDEX SY-TABIX TRANSPORTING VAL1 VAL2.

ELSE.

INSERT WA1 INTO ITAB2 INDEX SY-TABIX.

ENDIF.

ENDLOOP.

The above code uses BINARY SEARCH for collect semantics. READ BINARY runs in O( log2(n) ) time. The above piece of code can be more optimized by

LOOP AT ITAB1 INTO WA.

COLLECT WA INTO ITAB2.

ENDLOOP.

SORT ITAB2 BY K.

COLLECT, however, uses a hash algorithm and is therefore independent

of the number of entries (i.e. O(1)) .

Point # 9

APPEND LINES OF ITAB1 TO ITAB2.

This is more optimized as compared to

LOOP AT ITAB1 INTO WA.

APPEND WA TO ITAB2.

ENDLOOP.

Point # 10

DELETE ADJACENT DUPLICATES FROM ITAB COMPARING K.

This is much more optimized as compared to

READ TABLE ITAB INDEX 1 INTO PREV_LINE.

LOOP AT ITAB FROM 2 INTO WA.

IF WA = PREV_LINE.

DELETE ITAB.

ELSE.

PREV_LINE = WA.

ENDIF.

ENDLOOP.

Point # 11

DELETE ITAB FROM 450 TO 550.

This is much more optimized as compared to

DO 101 TIMES.

DELETE ITAB INDEX 450.

ENDDO.

12. Copying internal tables by using “ITAB2[ ] = ITAB1[ ]” as compared to “LOOP-APPEND-ENDLOOP”.

13. Specify the sort key as restrictively as possible to run the program faster.

Point # 12

ITAB2[] = ITAB1[].

This is much more optimized as compared to

REFRESH ITAB2.

LOOP AT ITAB1 INTO WA.

APPEND WA TO ITAB2.

ENDLOOP.

Point # 13

“SORT ITAB BY K.” makes the program runs faster as compared to “SORT ITAB.”

Internal Tables contd…

Hashed and Sorted tables

1. For single read access hashed tables are more optimized as compared to sorted tables.

2. For partial sequential access sorted tables are more optimized as compared to hashed tables

Hashed And Sorted Tables

Point # 1

Consider the following example where HTAB is a hashed table and STAB is a sorted table

DO 250 TIMES.

N = 4 * SY-INDEX.

READ TABLE HTAB INTO WA WITH TABLE KEY K = N.

IF SY-SUBRC = 0.

" ...

ENDIF.

ENDDO.

This runs faster for single read access as compared to the following same code for sorted table

DO 250 TIMES.

N = 4 * SY-INDEX.

READ TABLE STAB INTO WA WITH TABLE KEY K = N.

IF SY-SUBRC = 0.

" ...

ENDIF.

ENDDO.

Point # 2

Similarly for Partial Sequential access the STAB runs faster as compared to HTAB

LOOP AT STAB INTO WA WHERE K = SUBKEY.

" ...

ENDLOOP.

This runs faster as compared to

LOOP AT HTAB INTO WA WHERE K = SUBKEY.

" ...

ENDLOOP.

Former Member · ‎11-22-2007

if you need further information do let me know