SAP程序性能优化解析

For all entriesThe 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 thanrsdb/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∙FastThe Minus∙Difficult to program/understand∙Memory could be critical (use FREE or PACKAGE sizeSome 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_tabWHERE mykey >= i_tab-low and mykey <=i_tab-high.Nested selectsThe plus:o Small amount of datao Mixing processing and reading of datao Easy to code - and understandThe minus:o Large amount of datao when mixed processing isn’t neededo Performance killer no. 1Select using JOINSThe pluso Very large amount of datao Similar to Nested selects - when the accesses are planned by the programmer o In some cases the fastesto Not so memory criticalThe minuso Very difficult to program/understando Mixing processing and reading of data not possibleUse the selection criteriaSELECT * FROM SBOOK.CHECK: SBOOK-CARRID = 'LH' AND SBOOK-CONNID = '0400'.ENDSELECT.SELECT * FROM SBOOKWHERE CARRID = 'LH' ANDCONNID = '0400'.ENDSELECT.Use the aggregated functionsC4A = '000'.SELECT * FROM T100WHERE SPRSL = 'D' ANDARBGB = '00'.CHECK: T100-MSGNR > C4A.C4A = T100-MSGNR.ENDSELECT.SELECT MAX( MSGNR FROM T100 INTO C4A WHERE SPRSL = 'D' ANDARBGB = '00'.Select with viewSELECT * FROM DD01LWHERE 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 supportSELECT * FROM T100WHERE ARBGB = '00'AND MSGNR = '999'. ENDSELECT.SELECT * FROM T002.SELECT * FROM T100WHERE SPRSL = T002-SPRASAND ARBGB = '00'AND MSGNR = '999'.ENDSELECT. ENDSELECT.Select … Into tableREFRESH X006.SELECT * FROM T006 INTO X006.APPEND X006. ENDSELECTSELECT * FROM T006 INTO TABLE X006. Select with selection list SELECT * FROM DD01LWHERE DOMNAME LIKE 'CHAR%'AND AS4LOCAL = 'A'. ENDSELECTSELECT DOMNAME FROM DD01LINTO DD01L-DOMNAMEWHERE DOMNAME LIKE 'CHAR%'AND AS4LOCAL = 'A'.ENDSELECTKey access to multiple linesLOOP AT TAB.CHECK TAB-K = KVAL." ...ENDLOOP.LOOP AT TAB WHERE K = KVAL." ... ENDLOOP.Copying internal tablesREFRESH TAB_DEST.LOOP AT TAB_SRC INTO TAB_DEST. APPEND TAB_DEST. ENDLOOP.TAB_DEST[] = TAB_SRC[].Modifying a set of linesLOOP 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 linesDO 101 TIMES.DELETE TAB_DEST INDEX 450. ENDDO.DELETE TAB_DEST FROM 450 TO 550.Linear search vs. binaryREAD TABLE TAB WITH KEY K = 'X'.READ TABLE TAB WITH KEY K = 'X' BINARY SEARCH. Comparison of internal tablesDESCRIBE 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 databaseOptimizing 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 databaseserver 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.。