SAP程序性能优化解析

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

Some steps that might make FOR ALL ENTRIES more efficient:

?Removing duplicates from the driver table

?Sorting the driver table

?If possible, convert the data in the driver table to ranges so a BETWEEN statement is used instead of and OR statement:

FOR ALL ENTRIES IN i_tab

WHERE mykey >= i_tab-low and mykey <=

i_tab-high.

Nested selects

The plus:

o Small amount of data

o Mixing processing and reading of data

o Easy to code - and understand

The minus:

o Large amount of data

o when mixed processing isn’t needed

o Performance killer no. 1

Select using JOINS

The plus

o Very large amount of data

o Similar to Nested selects - when the accesses are planned by the programmer o In some cases the fastest

o Not so memory critical

The minus

o Very difficult to program/understand

o Mixing processing and reading of data not possible

Use the selection criteria

SELECT * FROM SBOOK.

CHECK: SBOOK-CARRID = 'LH' AND SBOOK-CONNID = '0400'.

ENDSELECT.

SELECT * FROM SBOOK

WHERE CARRID = 'LH' AND

CONNID = '0400'.

ENDSELECT.

Use the aggregated functions

C4A = '000'.

SELECT * FROM T100

WHERE SPRSL = 'D' AND

ARBGB = '00'.

CHECK: T100-MSGNR > C4A.

C4A = T100-MSGNR.

ENDSELECT.

SELECT MAX( MSGNR FROM T100 INTO C4A WHERE SPRSL = 'D' AND

ARBGB = '00'.

Select with view

SELECT * FROM DD01L

WHERE DOMNAME LIKE 'CHAR%'

AND AS4LOCAL = 'A'. SELECT SINGLE * FROM DD01T WHERE DOMNAME = DD01L-DOMNAME AND AS4LOCAL = 'A' AND AS4VERS = DD01L-AS4VERS AND DDLANGUAGE = SY-LANGU. ENDSELECT.

SELECT * FROM DD01V WHERE DOMNAME LIKE 'CHAR%' AND DDLANGUAGE = SY-LANGU. ENDSELECT.

Select with index support

SELECT * FROM T100

WHERE ARBGB = '00'

AND MSGNR = '999'. ENDSELECT.

SELECT * FROM T002.

SELECT * FROM T100

WHERE SPRSL = T002-SPRAS

AND ARBGB = '00'

AND MSGNR = '999'.

ENDSELECT. ENDSELECT.

Select … Into table

REFRESH X006.

SELECT * FROM T006 INTO X006.

APPEND X006. ENDSELECT

SELECT * FROM T006 INTO TABLE X006. Select with selection list SELECT * FROM DD01L

WHERE DOMNAME LIKE 'CHAR%'

AND AS4LOCAL = 'A'. ENDSELECT

SELECT DOMNAME FROM DD01L

INTO DD01L-DOMNAME

WHERE DOMNAME LIKE 'CHAR%'

AND AS4LOCAL = 'A'.

ENDSELECT

Key access to multiple lines

LOOP AT TAB.

CHECK TAB-K = KVAL.

" ...

ENDLOOP.

LOOP AT TAB WHERE K = KVAL.

" ... ENDLOOP.

Copying internal tables

REFRESH TAB_DEST.

LOOP AT TAB_SRC INTO TAB_DEST. APPEND TAB_DEST. ENDLOOP.

TAB_DEST[] = TAB_SRC[].

Modifying a set of lines

LOOP AT TAB.

IF TAB-FLAG IS INITIAL.

TAB-FLAG = 'X'.

ENDIF.

MODIFY TAB.

ENDLOOP.

TAB-FLAG = 'X'.

MODIFY TAB TRANSPORTING FLAG WHERE FLAG IS INITIAL.

Deleting a sequence of lines

DO 101 TIMES.

DELETE TAB_DEST INDEX 450. ENDDO.

DELETE TAB_DEST FROM 450 TO 550.

Linear search vs. binary

READ TABLE TAB WITH KEY K = 'X'.

READ TABLE TAB WITH KEY K = 'X' BINARY SEARCH. Comparison of internal tables

DESCRIBE TABLE: TAB1 LINES L1,

TAB2 LINES L2.

IF L1 <> L2.

TAB_DIFFERENT = 'X'.

ELSE.

TAB_DIFFERENT = SPACE.

LOOP AT TAB1.

READ TABLE TAB2 INDEX SY-TABIX.

IF TAB1 <> TAB2.

TAB_DIFFERENT = 'X'. EXIT.

ENDIF.

ENDLOOP.

ENDIF.

IF TAB_DIFFERENT = SPACE.

" ...

ENDIF.

IF TAB1[] = TAB2[].

" ...

ENDIF.

Modify selected components LOOP AT TAB. TAB-DATE = SY-DATUM. MODIFY TAB. ENDLOOP. WA-DATE = SY-DATUM. LOOP AT TAB. MODIFY TAB FROM WA TRANSPORTING DATE. ENDLOOP. Appending two internal tables LOOP AT TAB_SRC. APPEND TAB_SRC TO TAB_DEST. ENDLOOP APPEND LINES OF TAB_SRC TO TAB_DEST. Deleting a set of lines LOOP AT TAB_DEST WHERE K = KVAL. DELETE TAB_DEST. ENDLOOP DELETE TAB_DEST WHERE K = KVAL. Tools available in SAP to pin-point a performance problem The runtime analysis (SE30 SQL Trace (ST05 Tips and Tricks tool The performance database

Optimizing the load of the database Using table buffering Using buffered tables improves the performance considerably. Note that in some cases a statement can not be used with a buffered table, so when using these statements the buffer will be bypassed. These statements are: o o o o o Select DISTINCT ORDER BY / GROUP BY / HAVING clause Any WHERE clause that contains a sub query or IS NULL expression JOIN s A SELECT... FOR UPDATE If you wan t to explicitly bypass the buffer, use the BYPASS BUFFER addition to the SELECT clause. Use the ABAP SORT Clause Instead of ORDER BY The ORDER BY clause is executed on the database server while the ABAP SORT statement is executed on the application server. The database server will usually be the bottleneck, so sometimes it is better to move the sort from the database server to the application server. If you are not sorting by the primary key ( E.g. using the ORDER BY PRIMARY key statement but are sorting by another key, it could be better to use the ABAP SORT statement to sort the data in an internal table. Note however that for very large result sets it might not be a feasible solution and you would want to let the database

server sort it. Avoid the SELECT DISTINCT Statement As with the ORDER BY clause it could be better to avoid using SELECT DISTINCT, if some of the fields are not part of an index. Instead use ABAP SORT + DELETE ADJACENT DUPLICATES on an internal table, to delete duplicate rows.