Improving performance

[Former Member]

HI Experts,

If any reports taks too much time, then what r the step that I should tak for enhancing its performance. HOw this performance tunning works.

thanks.

Khan

[Former Member]

A lot of things matter..

Most important thing is to keep the interaction wid the database as less as possible..so avoid SELECTs within a LOOP.

Avoid nested LOOPs..

Avoid SELECT *

Various other things also which u can check in SE30..

Hope this helps..

Reward all helpful answers

[Former Member]

Hi Khan,

The main thing is the interaction to the Database should be as less a s possible.

Avoid the following:

1. loop within loop or nested loops

2. nested if .. endif

3. Select within a loop

4. Select * ( where only 25% of the fields are necessary)

5. Inner Joins ( not more than 2 tables )

Reward if Useful.

Regards,

Chitra

[Former Member]

hi,

You can see a report performance in SE30(Runtime analysis) and SQLtrace(ST05).

ST05 tells you the list of selected statements.

You should remember some points when you tuning the code:

- *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.

- *Generally, try to reduce I/O first, then memory, then CPU activity.

- *I/O operations that read/write to hard disk are always the most expensive operations. Memory, if not controlled, may have to be written to swap space on the hard disk, which therefore increases your I/O read/writes to disk. CPU activity can be reduced by careful program design, and by using commands such as SUM (SQL) and COLLECT (ABAP/4).

- 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.

- 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.

- Use as many table keys as possible in the WHERE part of your select statements.

- 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.

- 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.

- If the number of records you are reading is constantly growing, you may be able to break it into chunks of relatively constant size. For instance, if you have to read all records from 1991 to present, you can break it into quarters, and read all records one quarter at a time. This will reduce I/O operations. Test extensively with GET RUN TIME when using this method.

- Know how to use the 'collect' command. It can be very efficient.

- Use the SELECT SINGLE command whenever possible.

- 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.

Finally, try to avoid joins using more than 2 tables.

plz reward if useful....

[Former Member]

Check SQL and SE30. How long does you report need, and what would like to

get.

Total time = ABAP Time + DB Time

Check Top 10 in SQL (DB Time) where is potential for improvement?

Check Top 10 in SE30 (ABAP Time) where is potential for improvement?

When you know what consumes most of the time come back and ask for alternatives.

Siegfried

Read for SQL Trace:

/people/siegfried.boes/blog/2007/09/05/the-sql-trace-st05-150-quick-and-easy