SAP Performance & Tuning

SAP Performance & Tuning Bonus material for 201 ABAP Interview Questionshttp://www.201interviewquestions.com/books/abap.htm Material code : BM02 Author : P.Renjith Kumar Genie Press

1 The Architecture level to improve performance

The R/3 System has a three-layer client/server architecture,

With a Presentation layer, an Application layer and a Database layer.

The presentation layer and the application layer are scalable. This means that if there is a hardware bottleneck, you can extend the system by adding more front ends and application servers.

The database layer, as the central data repository, is not scalable.

Architecture One goal is to reduce the run time of programs on the application server, thereby reducing the CPU load.

Another goal is to reduce the database load. Reducing the database load is particularly important since the database software is not scalable.If the required data is in the R/3 buffers on the application server, accessing them requires approximately 0.1 milliseconds for each data record.

If the data records are read from the database buffer, around 1 millisecond is required.

When the data is read from the disk, this requires approximately 10 milliseconds for each data record. ABAP performance analysis areas of focus. An R/3 work process allocates around 5 MB of memory.

The R/3 table buffers allocate approximately 120 MB (40 MB for single record buffers, 80 MB for generic table buffers).

The data buffers of the database use around 500 MB of memory. The database on the disks can reach a size of several terabytes.

The data transfer between front end and application server occurs in blocks of 2 KB.

The transfer between application server and database server occurs in blocks of up to 32 KB. Memory Allocation in SAP Work process WPWPWP

WP

Roll areaWork ProcessTo DB server DispatcherQueueFrom presentation serverApplication server Response time: Time from the receipt of a user request to the sending of a response ( measured on the application server; does not include network time between the presentation server and the application server).

Dispatcher wait time: Time spent by the user request in the dispatcher queue.

Roll-in: Time required to roll the user context in to the R/3 work process.

Load time: Time required for loading and generating R/3 Repository or ABAP Dictionary objects.

Processing time: = response time - dispatcher wait time - roll-in - roll-out - load time - database time enqueue time - roll wait time

Enqueue time: Time from sending an enqueue request to the R/3 enqueue server to the receipt of the results General Definitions Database time: Time from sending an SQL statement to the receipt of the results (measured on the application server; includes network time between the application server and the database server).

Roll wait time: Time in which the user context is rolled out of the work process pending response to an RFC call. Roll-out: Time required to roll the user context in to the roll buffer.

CPU time: Time spent by the CPU in processing the transaction step (measured by the operating system; not an additive component of the response time).

Definitions Work Load Monitor

ST03 -> Performance Data base (Work Load Monitor )Select Server , Time .

If DB response > 600 ms then there is fundamental problem with R3 / DB . Initial Checks to be done to measure Performance

ST 03

DB 01

SM 50 SM50 ( Snap Shot analysis )To identify performance critical objects . To identify long running objects

How to identify long running process ?

Refresh the screen continuously , If a work process is there for a long time then it is long running process Important fields to know about the action to be done : Action / Table Snap Shot AnalysisCheck R3 based WP overview from ( SM50 )

Find long running WP and note its Action / Table field

Find Action ( Sequential / Direct / Insert )

Call DB Monitor ( DB01)

Check if any lock is there . If so find the user who is responsible and Tryto remove the lock , Or delete the lock .

Then based on the analysis go for SQL Trace / ABAP Run time analysis General Flow to get into tuning process Select Proper internal table types

Standard Tables : Used generally . Can be sorted

Sorted Tables Sorted automatically based on key

Hashed TablesUsed when I record is to be retreived . Good in performance . Work based on hash Key Initial Reporting considerationSe38 ->ABAP Debugger -> Settings ->Memory Display On

Debugger Finding Memory SE30 (Runtime Analysis) The runtime analysis is an additional development workbench tool that is quite useful for analyzing performance of an ABAP / 4 Program or transaction. With this tool, the system can display information about:

Executed instruction Accessed execution time. Tables and Types of access. Chronological execution flow

ST05 (SQL Trace) he SQL trace is a tool, which allows displaying and analyzing the contents for the database calls, which are made by the reports and transactions written in ABAP/4. It monitors programs and transactions on the database level. With the help of this facility for every open SQL instructions, you can display, about which SQL Embedded (DECLARE, OPEN, FETCH) Statement have been executed, besides analyzing the system performance.

SLIN or PROGRAM -> CHECK -> EXTENDED PROGRAM CHECK

ST03, ST02, ST04 are the tcode for workload, tuning and DB Performance Monitoring codes.

ST 05 ->SQL Trace -> Activate TraceGo back to SE 38 .

Then Run The program from SE38 ,

Now again Come back to ST05 , Deactivate trace .

Now press Display Trace . SQL TraceSQL Trace

Buffer Trace

Enquee Trace

RFC Trace ST05 Components

SQL Trace Internal Mechanism The goal of using an SQL Performance Trace is to find SQL statements with a high optimization potential. Use three user sessions. One user session is for the trace list, one for the compressed summary, and one for identical selects.

From the trace list you can access Explain SQL or the ABAP code. An expensive SQL statement is indicated when a database operation takes longer than 200,000 milliseconds, or when more than 10 FETCHes are required for a database operation.

In addition, a series of SQL statements that are similar in structure usually indicate nesting that can be optimized considerably. If the sum of SQL statements that are similar in structure take more than 200,000 milliseconds, they can be regarded as expensive.

SQL Trace Goals

SE30 -> Give Report name and Execute , Then click Analyze ,You will get DB time and ABAP run time

Run Time analysis

Run Time Analysis ( SE 30 )

Runtime analysis ( Comparing more 2 programs )

Very effective measure to increase performance in Select queries REPORT ZPR_PER_T1

TABLES : VBAK .

Data Begin of itab occurs 0 Include structure vbak data end of ITAB.

Select * from vbak into table itab .

Read table itab with key vbeln = '400151' .

REPORT ZPR_PER_T1 TABLES : VBAK .

Data Begin of itab occurs 0 . Include structure vbak .data end of ITAB.

Select * from vbak into table itab .

Read table itab with key vbeln = '400151' BINARY SEARCH.

Binary Search

First see runtime analysis ( SE30 ), try to make 50% of ABAP time and Database time.

Next SQL Trace (ST05), check which table is taking more time and try to minimize it by using full key or creating index for the where clause.

Next see logic in the program, try to avoid multiple reads on same table and try to minimize unnecessary data

Next try to remove for all entries if it has large amount of data in the for all entries internal table.

Next try to read Header table first than item table.

Next try to put joins

Next try to remove nested select's.

Steps to Improve Performance Select field in sequence as defined in database

free intrenal table memory wnen table is not required for further processing.

Steps to Improve Performance

Comparison of select statementsNot Recommended REFRESH TAB_DEST. LOOP AT TAB_SRC INTO TAB_DEST.APPEND TAB_DEST. ENDLOOP

Recommended

TAB_DEST[ ] = TAB_SRC[ ].

Some changes to statements to improve performance

Use already provided aggregate functions instead of manually coding it in ABAP.

Not Recommended

Maxnu = 0. Select * from zflight where airln = LF and cntry = IN.

Check zflight-fligh > maxnu.

Maxnu = zflight-fligh.

Endselect.

Recommended

Select max( fligh ) from zflight intmaxnu where airln = LF and cntry = IN.

Similary use MIN, AVG,COUNT,and SUM as needed.

Aggregate Function

Not Recommended

Refresh: itab_flight.

Select * from zflight into intab_flight.

Append intab_flight.

Clear intab_flight.

Endselect.

Recommended

Refresh: intab_flight.

Select * from zflight into table intab_flight

Avoid append statement Not Recommended

Loop at int_fligh.

If int_fligh-flag is initial.

Int_fligh-flag = X.

Endif.

Modify int_fligh.

Endloop.

Recommended

Int_fligh-flag = X.

Modify int_fligh transporting flag where flag is initial.

Modifying lines of internal table

Avoid using SELECT...ENDSELECT... construct and use SELECT ... INTO TABLE.

Use WHERE clause in your SELECT statement to restrict the volume of data retrieved.

Design your Query to Use as much index fields as possible from left to right in your WHERE statement

Either enable buffering in your database table or create Indexes to speed up the query.

5. Use FOR ALL ENTRIES in your SELECT statement to retrieve the matching records at one shot.

How to improve Performance Avoid using nested SELECT statement, SELECT within LOOPs.

Avoid using INTO CORRESPONDING FIELDS OF TABLE. Instead use INTO TABLE.

Avoid using SELECT * and Select only the required fields from the table.

Avoid nested loops when working with large internal tables.

10. Use assign instead of into in LOOPs for table types with large work areas How to improve PerformanceWhen in doubt call transaction SE30 and use the examples and check your code

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.

15. Use "MOVE" with individual variable/field moves instead of "MOVE-CORRESPONDING", creates more coding but is more effcient.

How to improve Performance SM51 App. Servers Overview STAT Display Statistical RecordsST05 SQL TraceSE30 Runtime AnalysisST03 Analysis of WorkloadDB02 Database Performance : Tables and Indexes.DB05 Analysis of Table w.r.t. Indexed FieldsST04 Database Performance Analysis : Oracle ViewSM66 Global Work Process Overview (Over All App Servers)SM50 Process Overview

Some useful Transactions related to performance analysis