Download SAP R/3 : ABAP/4 Development Code Efficiency Guidelines

SAP R/3 : ABAP/4 Development Code
Efficiency Guidelines
ABAP/4 (Advanced Business Application Programming 4GL) language is an "eventdriven", "top-down", well-structured and powerful programming language. The ABAP/4
processor controls the execution of an event. Because the ABAP/4 language incorporates
many "event" keywords and these keywords need not be in any specific order in the code,
it is wise to implement in-house ABAP/4 coding standards.
SAP-recommended customer-specific ABAP/4 development guidelines can be found
in the SAP-documentation. This page contains some general guidelines for efficient
ABAP/4 Program Development that should be considered to improve the systems
performance on the following areas:
Physical I/O - data must be read from and written into I/O devices. This can be a
potential bottle neck. A well configured system always runs 'I/O-bound' - the
performance of the I/O dictates the overall performance.

Memory consumption of the database resources eg. buffers, etc.

CPU consumption on the database and application servers

Network communication - not critical for little data volumes, becomes a bottle
neck when large volumes are transferred.
Policies and procedures can also be put into place so that every SAP-customer
development object is thoroughly reviewed (quality – program correctness as well as
code-efficiency) prior to promoting the object to the SAP-production system.
Information on the SAP R/3 ABAP/4 Development Workbench programming tools and
its features can be found on the SAP Public Web-Server.
CLASSIC GOOD 4GL PROGRAMMING CODE-PRACTICES
GUIDELINES

Avoid dead-code

Remove unnecessary code and redundant processing

Spend time documenting and adopt good change control practices

Spend adequate time anayzing business requirements, process
flows, data-structures and data-model

Quality assurance is key: plan and execute a good test plan and
testing methodology

Experience counts
SELECT * FROM <TABLE>
CHECK: <CONDITION>
ENDSELECT
vs.
SELECT * FROM <TABLE>
WHERE <CONDITION>
ENDSELECT
In order to keep the amount of data which is relevant to the query the hit set
small, avoid using SELECT+CHECK statements wherever possible. As a general rule of
thumb, always specify all known conditions in the WHERE clause (if possible). If there
is no WHERE clause the DBMS has no chance to make optimizations. Always specify
your conditions in the Where-clause instead of checking them yourself with checkstatements. The database system can also potentially make use a database index (if
possible) for greater efficiency resulting in less load on the database server and
considerably less load on the network traffic as well.
Also, it is important to use EQ (=) in the WHERE clause wherever possible, and
analyze the SQL-statement for the optimum path the database optimizer will utilize via
SQL-trace when necessary.
Also, ensure careful usage of "OR", "NOT" and value range tables (INTTAB) that
are used inappropriately in Open SQL statements.
SELECT *
vs.
SELECT SINGLE *
If you are interested in exactly one row of a database table or view, use the
SELECT SINGLE statement instead of a SELECT * statement. SELECT SINGLE
requires one communication with the database system whereas SELECT * requires two.
SELECT * FROM <TABLE> INTO <INTTAB>
APPEND <INT-TAB>
ENDSELECT
vs.
SELECT * FROM <TABLE> INTO
TABLE <INT-TAB>
It is usually faster to use the INTO TABLE version of a SELECT statement than
to use APPEND statements
SELECT ... WHERE + CHECK
vs.
SELECT using aggregate function
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 within the program. The RDBMS is responsible for aggregated computations
instead of transferring large amount of data to the application. Overall Network,
Application-server and Database load is also considerably less.
SELECT INTO TABLE <INT-TAB> +
LOOP AT T
…………
SELECT * FROM <TABLE> INTO
TABLE <INT-TAB>.
LOOP AT <INT-TAB>.
ENDLOOP.
vs.
SELECT * FROM <TABLE>
……….
ENDSELECT
If you process your data only once, use a SELECT-ENDSELECT loop instead of
collecting data in an internal table with SELECT ... INTO TABLE. Internal table
handling takes up much more space
Nested SELECT statements:
SELECT * FROM <TABLE-A>
SELECT * FROM <TABLE-B>
……..
ENDSELECT.
ENDSELECT
vs.
Select with view
SELECT * FROM <VIEW>
ENDSELECT
To process a join, use a view wherever possible instead of nested SELECT
statements.
Using nested selects is a technique with low performance. The inner select statement is
executed several times which might be an overhead. In addition, fewer data must be
transferred if another technique would be used eg. join implemented as a view in ABAP/4
Repository.
· SELECT ... FORM ALL ENTRIES
· Explicit cursor handling (for more information, goto Transaction SE30 – Tips & Tricks)
Nested select:
SELECT * FROM pers WHERE condition.
SELECT * FROM persproj WHERE
person = pers-persnr.
... process ...
ENDSELECT.
ENDSELECT.
vs.
SELECT persnr FROM pers INTO TABLE
ipers WHERE cond. ……….
SELECT * FROM persproj FOR ALL
ENTRIES IN ipers
WHERE person = ipers-persnr
………... process .……………
ENDSELECT.
In the lower version the new Open SQL statement FOR ALL ENTRIES is used. Prior
to the call, all interesting records from 'pers' are read into an internal table. The second
SELECT statement results in a call looking like this (ipers containing: P01, P02, P03):
(SELECT * FROM persproj WHERE person = 'P01')
UNION
(SELECT * FROM persproj WHERE person = 'P02')
UNION
(SELECT * FROM persproj WHERE person = 'P03')
In case of large statements, the R/3's database interface divides the statement into
several parts and recombines the resulting set to one. The advantage here is that the
number of transfers is minimized and there is minimal restrictions due to the statement
size (compare with range tables).
SELECT * FROM <TABLE>
vs.
SELECT <column(s)> FROM <TABLE>
Use a select list or a view instead of SELECT *, if you are only interested in specific
columns of the table. If only certain fields are needed then only those fields should be
read from the database. Similarly, the number of columns can also be restricted by using
a view defined in ABAP/4 Dictionary. Overall database and network load is considerably
less.
SELECT without table buffering support
vs.
SELECT with table buffering support
For all frequently used, read-only(few updates) tables, do attempt to use SAPbuffering for eimproved
performance response times. This would reduce the overall Database activity and
Network traffic.
Single-line inserts
LOOP AT <INT-TAB>
INSERT INTO <TABLE> VALUES <INTTAB>
ENDLOOP
vs.
Array inserts
Whenever possible, use array operations instead of single-row operations to
modify the database tables
Frequent communication between the application program and database system produces
considerable overhead
Single-line updates
SELECT * FROM <TABLE>
<COLUMN-UPDATE STATEMENT>
UPDATE <TABLE>
ENDSELECT
vs.
Column updates
UPDATE <TABLE> SET <COLUMNUPDATE STATEMENT>
Wherever possible, use column updates instead of single row updates to update
your database tables
DO....ENDDO loop with Field-Symbol
vs.
Using CA operator
Use the special operators CO, CA, CS instead of programming the operations
yourself
If ABAP/4 statements are executed per character on long strings, CPU consumprion can
rise substantially
Use of a CONCATENATE function
module
vs.
Use of a CONCATENATE statement
Some function modules for string manipulation have become obsolete, and should
be replaced by ABAP statements or functions
STRING_CONCATENATE... ---> CONCATENATE
STRING_SPLIT... ---> SPLIT
STRING_LENGTH... ---> strlen()
STRING_CENTER... ---> WRITE..TO. ..CENTERED
STRING_MOVE_RIGHT ---> WRITE...TO...RIGHT-JUSTIFIED
Moving with offset
vs.
Use of the CONCATENATE statement
Use the CONCATENATE statement instead of programming a string
concatenation of your own
Use of SEARCH and MOVE with offset
vs.
Use of SPLIT statement
Use the SPLIT statement instead of programming a string split yourself
Shifting by SY-FDPOS places
vs
Using SHIFT...LEFT DELETING
LEADING...
If you want ot delete the leading spaces in a string use the ABAP/4 statements
SHIFT...LEFT DELETING LEADING... Other constructions (with CN and SHIFT...
BY SY-FDPOS PLACES, with CONDENSE if possible, with CN and ASSIGN
CLA+SY-FDPOS(LEN) ...) are not as fast
Get a check-sum with field length
vs
Get a check-sum with strlen ()
Use the strlen () function to restrict the DO loop to the relevant part of the field, eg.
when determinating a check-sum
Quick Note on Design of secondary database indexes
First it must be stated that table design is a more logical work while index design is
rather technical. In table design it might make sense to place certain fields (client,
company code, ...) in the beginning. In index design, this is not advisable. Very
important for an index is that it contains very selective fields in the beginning. Those are
fields like object numbers. Not selective are client, company code, ...

Indexes should be small (few fields). The Database optimizer can combine two or
more indexes to execute a query.

Indexes of one table should be disjoint (have few common fields), in order not to
confuse the optimizer which index to use.
Note that each index slows the inserts into the table down. Updates are only slowed
down if indexed fields are updated. In general, heavy inserted tables should have only
few indexes while heavy selected tables might have more.
Quick Note on Design of logical databases
Using logical databases is a good method to write reports. Logical databases can be
optimized centrally. But ensure that the structure of the logical database fits well to your
report. Otherwise the effect can be the opposite.
For more information about more SAP ABAP/4 Development code-efficiency
standards, esp. on non-database related tips and tricks, please goto transaction SE30 and
click on Tips & Tricks section, which served as the main source of reference for this
section of this document.
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