ABAP Performance DOs and DON'Ts

DO DON’T Additional InfoStandard and Hashed internal table types.

Sorted internal table type.

Use a hashed table whenever many single record accesses are required for an internal table via a fully specified key.

READ on sorted standard table using ‘BINARY SEARCH’.

  READ without BINARY SEARCH on a standard table forces sequential read.

Addition TRANSPORTING on READ and MODIFY

  Reduces unwanted copy

overheads. Parallel Cursor Nested Loop Use Parallel cursor

technique when implementing nested loops.

  WHERE clause on internal table operations e.g.

LOOP, MODIFY, etc.

Use index operations like LOOP AT …FROM …TO and MODIFY …FROM …TO

  DELETE WHERE in a LOOP.

Instead, mark for deletion using MODIFY in a LOOP. Perform mass delete using DELETE WHERE after the loop.

  SORT inside a LOOP Sort is an expensive ABAP statement. It should be use outside of a loop.

  DELETE or SORT on a hashed table

Memory needed to maintain a hashed index increases.

Table pointers for MOVE, COMPARE and mass internal table operations

  Operations such as itab1[] = itab2[]

Addition ASSIGNING for internal table modification and processing.

  Use of ASSIGNING eliminates copy overhead.

Pass internal tables into subroutines by reference

  Passing by value results in data and memory duplication.

Free internal tables   Free internal tables when they are not needed in the subsequent program steps.

Use assignment operator Move Corresponding  

Typed field symbols.   The runtime of a typed ASSIGN statement is around 40% less than that required for an equivalent untyped ASSIGN statement.

How to improve the performance of ABAP Program.

1. Always check the driver internal tables is not empty, while using FOR ALL ENTRIES

2. Avoid for all entries in JOINS

3. Try to avoid joins and use FOR ALL ENTRIES.

4. Try to restrict the joins to 1 level only ie only for tables

5. Avoid using Select *.

6. Avoid having multiple Selects from the same table in the same object.

7. Try to minimize the number of variables to save memory.

8. The sequence of fields in 'where clause' must be as per primary/secondary index

9. Avoid creation of index as far as possible

10. Avoid operators like <>, > , < & like % in where clause conditions 11. Avoid select/select single statements in loops. 12. Try to use 'binary search' in READ internal table. Ensure table is sorted before using BINARY SEARCH. 13. Avoid using aggregate functions(SUM, MAX etc) in selects( GROUP BY,HAVING,) 14. Avoid using ORDER BY in selects. 15. Avoid Nested Selects 16. Avoid Nested Loops of Internal Tables 17. Try to use FIELD SYMBOLS. 18. Try to avoid into Corresponding Fields of 19. Avoid using Select Distinct, Use DELETE ADJACENT Note: Also by going to transaction SE30->tips and tricks you can get the idea

Performance Optimization

Q) What is "Performance Tuning"? Why do we need it?

Depending on the complexity and volumes of data, ABAP programs often are vulnerable to time-out issues and short dumps. Users, in general (SAP/Non SAP) get annoyed by time consumiung applicationsas they (the programs) often affect user productivity, TCO of software and many more critical factors pertaining to the management of the software. This is where the need "Performance Tuning" arises.

So, what exactly is Performance Tuning?

This simply means - ensuring that an ABAP program performs efficiently. A good ABAP program to bring the desired output to the user within the desired timeframe. Thus increasing the productivity of users, saving a lot of time and keeping the management happy in the bargain.

Q) List out the benefits of Performance Tuning/Optimization.

Maximum user productivity Minimum time-outs Lower total cost of ownership - due to reduced timelines and increased productivity

of users Faster ROI (return on investment) Easier upgradation

Q) List out the steps for Performance Tuning/Optimization.

Data declaration

Remove all code and variables that are not used in the program Avoid declaring internal tables using LIKE or TYPE reference. Instead, use BEGIN

OF... ... END OF ITAB. Avoid declaring internal tables using 'occurs 0' & 'with header line'

SELECTs & DB access

Use selection criteria to effectively select and limit the number of database reads Select only those columns that are needed – Do not use a SELECT * unless necessary To populate an internal table thru a SELECT, use the INTO TABLE addition To update table entries, specify the columns Design your SELECT Query to Use as much index fields as possible from left to right

in your WHERE statement Use a SELECT SINGLE if the primary keys are known, otherwise SELECT UPTO 1 ROWS Do not use nested SELECTs – Use views, joins or the FOR ALL ENTRIES option Avoid using INTO CORRESPONDING FIELDS OF TABLE. Instead use INTO TABLE. Do not use SELECTs in loops Restrict the database access by using the WHERE clause – do not use a CHECK Use indexes wherever available Avoid NOT in the WHERE condition Do not select the same data more than once Avoid the SELECT DISTINCT Statement. Instead use ABAP SORT + DELETE ADJACENT

DUPLICATES on an internal table, to delete duplicate rows.

Processing data

Use aggregate functions wherever required instead of additional logic Use sort on the internal table for small amounts of data and database ORDER BY for

larger amount Whenever using READ TABLE use BINARY SEARCH addition to speed up the search.

Be sure to sort the internal table before binary search. Use "CHECK" instead of IF/ENDIF whenever possible. Use "CASE" instead of IF/ENDIF whenever possible. Use "MOVE" with individual variable/field moves instead of "MOVE-CORRESPONDING"

Performing Checks

Perform the Extended Program Check Perform Runtime Analyses

Q) List out the tools used Performance Tuning/Optimization.

Run time analysis transaction SE30This transaction gives all the analysis of an ABAP program with respect to the database and the non-database processing.

SQL Trace transaction ST05The trace list has many lines that are not related to the SELECT statement in the ABAP program. This is because the execution of any ABAP program requires additional administrative SQL calls. To restrict the list output, use the filter introducing the trace list.

ABAP Performance Tuning Tips

Tools that can be used to help with performance tuning.1. ST05 is the performance trace. It contains the SQL Trace plus RFC, enqueue and buffer trace. Mainly the SQL trace is is used to measure the performance of the select statements of the program.

2. SE30 is the Runtime Analysis transaction and can be used to measure the application performance.

3. SAT transaction is the replacement SE30. It provides same functionality as SE30 plus some additional features.

4. ST12 transaction (part of ST-A/PI software component) is a combination of ST05 and SAT. Very powerful performance analysis tool used primarily by SAP Support.

5. One of the best tools for static performance analyzing is Code Inspector (SCI). There are many options for finding common mistakes and possible performance bottlenecks.

Steps to optimize the ABAP Code

1. Databasea. Use WHERE clause in your SELECT statement to restrict the volume of data retrieved.  b. Design the Query to use as many index fields as possible from left to right in the WHERE statementc. Use FOR ALL ENTRIES in your SELECT statement to retrieve the matching records at one shotd. Avoid using nested SELECT statement and SELECT within LOOPs, better use JOINs or FOR ALL ENTRIES. Use FOR ALL ENTRIES when the internal table is already there. Try JOINs if the SELECT statements are right behind each other.e. Avoid using ORDER BY in SELECT statements if it differs from used index  (instead, sort the resulting internal table), because this may add additional work to the database system which is unique, while there may be many ABAP serversf. INDEX: Creation of Index for improving performance should not be taken without thought. Index speeds up the performance but at the same time adds two overheads namely; memory and insert/append performance. When INDEX is created, memory is used up for storing the index and index sizes can be quite big on large transaction tables! When inserting a new entry in the table, all the indices are updated. More indices, more time. More the amount of data, bigger the indices, larger the time for updating all the indicesg. Avoid Executing an identical Select (same SELECT, same parameter) multiple times in the programh. Avoid using join statements if adequate standard views exist.

2. Table Buffera. Defining a table as buffered (SE11) can help in improving the performance but this has to be used with caution. Buffering of tables leads to data being read from the buffer rather than from table. Buffer sync with table happens periodically, only if something changes. If this table is a transaction table chances are that the data is changing for particular selection criteria, therefore application tables are usually not suited for table buffering. Using table buffering in such cases is not recommended. Use Table Buffering for configuration data and sometimes for Master Data b.  Avoid using complex Selects on buffered tables, because SAP may not be able to interpret this request, and may transmit the request to the database. The code inspector tells which commands bypass the buffer.

3. Internal Tablea. Use sorted tables when nested loops are required.b. Use assign (field symbol) instead of into in LOOPs for table types with large work areasc. Use READ TABLE BINARY SEARCH with large standard tables speed up the search. Be

sure to sort the internal table before binary search. d. Use transaction SE30 to check the code

4. Miscellaneousa. PERFORM: When writing a subroutine, always provide type for all the parameters. This reduces the overhead which is present when the system determines on its own each type from the formal parameters that are passed.

Which is the better - JOINS or SELECT... FOR ALL ENTRIES?The effect of FOR ALL ENTRIES needs to be observed first by running a test program and analyzing SQL trace. Certain options set by BASIS can cause FOR ALL ENTRIES to execute as an 'OR' condition. This means if the table being used FOR ALL ENTRIES has 3 records, SQL Trace will show 3 SQLs getting executed. In such a case using FOR ALL ENTRIES is useless. However of the SQL Trace shows 1 SQL statement it's beneficial since in this case FOR ALL ENTRIES is actually getting executed as an IN List.JOINS are recommended to be used till 5 joins. If the JOIN is being made on fields which are key fields in both the tables, it reduced program overhead and increases performance. So, if the JOIN is between two tables where the JOINING KEYS are key fields JOIN is recommended over FOR ALL ENTRIES.

You can use for all entries to reduce the database hits, and use non-key fields.Here is a code with join:

SELECT A~VBELN A~KUNNR A~KUNAG B~Name1into table i_likpFROM LIKP AS A  INNER JOIN KNA1 AS B    ON A~kunnr = B~KUNNR.* For with limited data using for all entries:* Minimize entries in I_likp by deleting duplicate kunnr.LOOP AT i_likp INTO w_likp.  w_likp2-KUNAG = w_likp-KUNAG.  APPEND w_likp2 TO i_likp2.ENDLOOP.SORT i_likp2 BY kunnr.DELETE ADJACENT DUPLICATES FROM i_likp2 COMPARING kunnr.* GET DATA FROM kna1IF NOT i_likp2[] IS INITIAL.  SELECT kunnr name1    INTO TABLE i_kna1    FROM kna1    FOR ALL ENTRIES IN i_likp2    WHERE kunnr = i_likp2-KUNNR.ENDIF.

Avoid use of nested loopsWhen a nested loop has to be used, use a condition for the inner loop.  Otherwise in the production environment it may be possible that the loop takes a lot of time and dumps.loop at itab1.  loop at itab2 where f1 = itab1-f1.  ....  endloop.end loop.Another option is to use READ with BINARY SEARCH for the second table.SORT itab2 BY f1.loop at itab1.  Read table itab2 with key f1 = itab1-f1 BINARY SEARCH.   if sy-subrc = 0.    idx = sy-tabix.    loop at itab2 from idx.      if itab2-f1 <> itab1-f1.        exit.      endif.     ....    endloop.  endif.endloop.

SAP ABAP Fine Tuning Developments

Factors influencing Performance Tuning§          Database Operation§          Application Code§          Memory Handling§          Tools for Tuning-          SQL Trace-          Runtime AnalysisDatabase Operation§          Database Access§          Data volume and Network Load§          Bulk retrieval or update§          Frequency of Communication between Application Program & Database System (Array operation over Single Row)§          Usage of Index§          Table bufferingDesign Stage Considerations§          Restrict Data Selection§          Make more mandatory fields..§          If initial data selection itself is huge.-          warn user about performance before proceeding further-          Terminate further processing with suggestion to run with more restriction

-          Suggest Background operation§          Designing the selection screen :-          Correctly group the fields which are used for filtering the data during selection.-          group the fields which would be used for only restricting the output.User then would know, which can improve response and which cannot.§          If the report is used for on-line purpose only, drill down report would be better alternative.§          Get more information only when you need it!§          Check current data size and the expected growth rate.Effective Select Statement§          Specify by Key fields while selection§          Avoid select within loops / select.. Endselect§          Inner join / views better than nested selects / multiple selects§          Take care 'For All Entries in Table'-          Initial or Not-          Large number of records§          Keep Select Clause simple§          Into Corresponding Fields Vs Into TableData Selection from database§          INTO TABLE with the SELECT statement provides faster access to the database than using an APPEND statement with SELECT§          The INTO TABLES statement groups the records which accounts for reduction in network traffic whereas  APPEND statements access the DATABASE for individual records§          For data which is used once the SELECT  ENDSELECT loop is effective since  the INTO TABLE statement collects  all the data of a table in the memory§          Use package size option, Data is put in table in packets of size n§          Use "where" clause with index rather than select all and checkAggregate Clauses§          Use ORDER BY Clauses only if indexes are taken§          Do not use ORDER BY if data selected is more ( more than 20% of total )§          Statements like COUNT, SUM, MIN,  MAX, AVG are done at the database level§          Usage of these statements avoid  transferring large amounts of data to an application for calculating its aggregate§          These aggregate functions can also be combined well with the GROUP BY statementINDEXES    •          An index can be considered a sorted  copy of a database table of certain fields.•           Sorting provides faster access to the data records of the table, ( binary search ).•           Indexes are of two types:- Primary and Secondary•          .The primary index contains the key fields of the table and a pointer to the non-key fields•           The primary index is created automatically when the table is created in the database.•           Other indexes created are called secondary indexes.•           Table is accessed frequently with fields other than fields of primary indexProgramming using Indexes

§          Data being selected§          Volume of data§          Order of fields in Index

What to Keep in Mind for Secondary Indexes                                §          When table contents change, indexes are readjusted§          Slows down database insertion§          Frequently accessed tables should not have too many indexes§          Create indexes only when that index is likely to be used frequently§          Indexes created may not be used to one's liking.§          Determined by database optimizer by an algorithm§          Indexes should have few common fields. Too many common fields would   create problems for the optimizer§          Use SQL Trace for determining indexesType of Index Scans§          Unique Index Scan :- The entry specified by that index is unique§          Range Scan:-              Most frequent, a range of values scanned§          Full Table Scan:-          No index used, full table scanned for dataBuffering - Important Points to consider§          The database interface of SAP provides buffers on each application server which allows local storage of database tables§          Access to data in tables which are buffered can take place from application server instead of accessing the database directly§          Table buffers enhance the performance of a system by reducing the number of times the database is accessed through the network for data§          The performance improvement due to table buffers on a systems with several application servers is considerably more compared to a central system with only one application server§          But on a central system with one application server a noticeable effect on the performance comes due the reduction in the number of processes when a buffer is accessed instead the database§          The buffer values remain unchanged when a read access is  made. If the application changes the data the changes are made on the database and then the buffer on the corresponding application server§          When data is changed on the database it is logged in the DDLOG table on the database§          Buffers on other application servers  are updated at  intervals of one to two minutes§          This is done with the help of the log maintained in the DDLOG table. When the synchronizing mechanism is run, the log invalidates the buffers on all other application servers§          This causes all the other application servers to access the database directly for data and update their buffers the next time when data is neededOperations on Internal Tables§          Copying of Internal Tables - Copy whole table rather than line by line§          Do not delete records of the same internal table within loop§          Delete records using where clauseMemory Management§          Avoid unnecessary variables§          Use local variables in modularization units

§          Transfer key information to the Calls§          Free Internal table no longer in use§          Optimize usage of bulk data, memory and processing overheadSQL Trace (ST05)§          Overview§          Understanding What is Measured§          Creating an SQL Trace Data File§          Calling an SQL Trace Data File §          Analyzing an SQL Trace Data FileSQL Trace: Overview§          The SQL statements that the application uses.§          Shows what the ABAP processor is requesting from the database§          Lists actual duration of each database request§          What database accesses or changes occur in the update section of the application§          How the system translates ABAP OPEN SQL commands (such as SELECT) into standard SQL commands§          Gives index usage and available indexes§          Presents types of table scans used on fields§          Red flags questionable SQL statements§          Where the application makes unnecessary database accesses or repeated accesses§          Gives index usage and available indexes§          Presents types of table scans used on fields§          Red flags questionable SQL statements§          Where the application makes unnecessary database accesses or repeated accessesFrom the time the trace function is turned on to the time it is turned off again, all database activity occurring either for a specific user or for an entire system is recorded. The SQL Trace tool measures the following database requests:Buffering of Database Requests-          To keep the number of runtime-consuming PREPARE calls small, each an application's work processes hold a certain number of already translated SQL statements in a special buffer. By default, a process holds up to 250 statements.-          If the system must execute a specific OPEN SQL, the system first checks whether this statement is stored in the "statement cache". If the statement is in the cache, the system executes it immediately using a REOPEN (SELECT) or a REEXEC (INSERT, UPDATE, DELETE).Buffering of Database Requests (cont'd)-          If the statement is not buffered, a PREPARE operation prepares it for the subsequent OPEN/EXEC. The system administers the buffer according to the LRU algorithm ("least recently used"). When space is needed for new statements, the statements that are rarely used are deleted. As a result of the LRU algorithm, the statement must prepare frequently used statements usually only once.-          An application server buffers the DECLARE, PREPARE, OPEN, and EXEC requests within the cursor cache of one work process. As a result, once the system opens a cursor for a DECLARE operation, it can use this cursor over and over again within the same work process.Understanding What is Measured§          Logical Sequence of Database Requests

-          Database requests are interconnected and always occur in the same logical sequence. The DECLARE function defines and numbers the cursor. DECLARE precedes the PREPARE function. Use PREPARE to prepare a specific database statement, such as:-          select * from sflight where carrid eq 'LH'.-          and define the access method before the system can transfer the request to the database. During this preparation, the system is concerned only with the structure of the SQL statement and not with the values it contains.-          The OPEN function takes the prepared SELECT statement and completes it with the correct values. In the above example, OPEN would issue the field carrid the value LH.Creating an SQL Trace Data File§          Go to the program to be SQL traced§          If the program has a selection screen, execute the program and bring it to the selection screen§          From the menu, choose System > Create Session, and type /nst05 in the transaction entry field of the new session.  Select the Trace on button.§          Go back to the program session, and execute the program (F8).  Once the program is through executing, return to the SQL Trace session and select Trace off.  Now select List Trace.   A detailed list of all database requests will appear, as shown on the next slide.Retrieving Trace Data File1) Call up the initial screen of the SQL Trace tool.2) Choose List trace.           The system asks to specify a trace file. The last trace that was run is suggested as the default value.3) Ensure that the information is correct.           If a trace is run using an * (asterisk) for the user name, enter * (asterisk) in the DB trace for user to retrieve the trace.4) Choose OK.General Tips§          Visualize table growth and build suitable restrictions while on drawing board itself like limiting document selection by date / status / material etc.§          SELECT less with right where clause than selecting all and then filtering.§          Use effective table joins or use correct views.§          Reduce database hits by selecting all info. in one shot rather than repeated access.§          Use of secondary sales table may reduce time instead using main table and using custom indices.§          Check whether right index is picked§          Apply all performance related techniques while processing internal tables, especially when they are expected to be big.§          Perform run time analysis and SQL trace to identify bottle necks