ABAP/4 Optimization
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Use the GET RUN TIME command to help evaluate performance.
It's hard to know whether that optimization technique REALLY helps unless you
test it out. Using this tool can help you know what is effective, under what
kinds of conditions. The GET RUN TIME has problems under multiple CPUs, so you
should use it to test small pieces of your program, rather than the whole program.
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Avoid 'SELECT *', especially in tables that have a lot of
fields. Use SELECT A B C INTO instead, so that fields are only read if they are
used. This can make a very big difference.
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Field-groups can be useful for multi-level sorting and
displaying. However, they write their data to the system's paging space, rather
than to memory (internal tables use memory). For this reason, field-groups are
only appropriate for processing large lists (e.g. over 50,000 records). If you
have large lists, you should work with the systems administrator to decide the
maximum amount of RAM your program should use, and from that, calculate how
much space your lists will use. Then you can decide whether to write the data
to memory or swap space. See the Fieldgroups ABAP example.
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Use as many table keys as possible in the WHERE part of your
select statements.
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Whenever possible, design the program to access a relatively
constant number of records (for instance, if you only access the transactions
for one month, then there probably will be a reasonable range, like 1200-1800,
for the number of transactions inputted within that month). Then use a SELECT A
B C INTO TABLE ITAB statement.
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Get a good idea of how many records you will be accessing.
Log into your productive system, and use SE80 -> Dictionary Objects (press
Edit), enter the table name you want to see, and press Display. Go To Utilities
-> Table Contents to query the table contents and see the number of records.
This is extremely useful in optimizing a program's memory allocation.
¨
Try to make the user interface such that the program
gradually unfolds more information to the user, rather than giving a huge list
of information all at once to the user.
¨
Declare your internal tables using OCCURS NUM_RECS, where
NUM_RECS is the number of records you expect to be accessing. If the number of
records exceeds NUM_RECS, the data will be kept in swap space (not memory).
¨
Use SELECT A B C INTO TABLE ITAB whenever possible. This
will read all of the records into the itab in one operation, rather than
repeated operations that result from a SELECT A B C INTO ITAB... ENDSELECT
statement. Make sure that ITAB is declared with OCCURS NUM_RECS, where NUM_RECS
is the number of records you expect to access.
¨
Many tables contain totals fields (such as monthly expense
totals). Use these avoid wasting resources by calculating a total that has
already been calculated and stored.
¨
Program Analysis Utility
To determine the usage of variables and
subroutines within a program, you can use the ABAP utility called ‘Program
Analysis’ included in transaction SE38. To do so, execute transaction SE38,
enter your program name, then use the path Utilities -> Program Analysis
ABAP
PERFORMANCE IMPROVEMENTS VIA DATA DICTIONARY
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INDEX CREATION SUGGESTIONS RELATED TO DATABASE PERFORMANCE
·
The columns at the beginning of an index are the most “common”. The most
“common” columns are those where reports are selecting columns with no ranges -
the where clause for these columns is an “equal to” expression. Rearrange
columns of an index to match the selection criteria. For example, if a select
statement is written to include columns 1 and 2 with “equal to” expressions in
the where clause and column 3 and 4 are selected with value ranges, then the
index should be created with columns in the sequence of 1,2,3,4.
·
Columns towards the end of the index are either infrequently used in selects or
are part of reporting selects that involve ranges of values.
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TABLE TYPE SUGGESTIONS RELATED TO DATABASE PERFORMANCE
·
Use VIEW tables to effectively join and “denormalize” related tables that are
taking large amounts of time to select for reporting. For example, at times
where highly accessed tables normalize description text into one table and the
header data into another table, it may make sense to create a view table that
joins the relevant fields of the two associated with a poor performing ABAP.
¨
For POOL tables that contain large amounts of data and are
highly accessed, convert the pooled table into a transparent table and add an
index. POOLED tables are supposed to be collections of smaller tables that are
quickly accessed from the database or are completely buffered in memory.
Pooled tables containing more than a few hundred rows and are accessed many
times in a report or transaction are candidates for POOL to TRANSPARENT
Conversion. For example, table A053 contains tax jurisdiction condition
information and are accessed more than ten times in the sales order create
transaction. If the entire United States tax codes are loaded into these
condition tables, the time to save a sales order increases to unacceptable
levels. Converting the tax condition table to transparent and creating an
index based upon the key fields, decreases processing time from minutes to
seconds.
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Do not allow the use of LIKE in an SAP SQL statement accessing a large
table.
·
Use internal tables in ABAPs to preselect values once and store values in
memory for sorting and searching purposes (this is an assumption stated at the
beginning of this discussion).
·
Avoid logical databases when not processing all row s of a table. In fact, a
logical database is merely a group of nested SAP SQL SELECT statements. In
general, when processing a small number of rows in a larger table is required,
the use of internal tables and NOT using a logical database or nested selects
will be much better for performance.
ABAP IMPORTANT REPORTS
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RSBDCBTC
Submit a BDC
job with an internal batch number and wait for the end of the batch input
session.
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RSBDCSUB
Release batch
input sessions automatically
ABAP IMPORTANT TCODES
OSS1
SAP Online Service System
SM13
Update monitor. Will show update tasks status. Very useful to determine
why an
update failed.
S001 ABAP Development Workbench
SE01 Old Transport & Corrections
screen
SE10 New Transport & Correction
screen
SE09 Workbench Organizer
SE16 Data Browser: Initial Screen.
SE30 ABAP/4 Runtime Analysis
SE36 ABAP/4: Logical Databases
SE37 ABAP/4 Function Modules
SE38 ABAP Editor
SE39 Splitscreen Editor: Program
Compare
SE41 Menu Painter
SE51 Screen Painter: Initial Screen.
SE71 SAPscript layout set
SE80 ABAP/4 Development Workbench
Object Browser
SM12 Lock table entries (unlock locked
tables)
SM21 View the system log, very useful
when you get a short dump. Provides much
more info than short dump
SM35 View Batch Input Sessions
SQ00 ABAP/4 Query: Start Queries
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