What is the Faster way in modifying an internal table inside a loop

Hello Abap Gurus,

I would like to know which one performs faster.

(1)

LOOP AT itab.

itab-f1 = 'X'.

MODIFY itab INDEX sy-tabix.

ENDLOOP.

OR

(2)

LOOP AT itab ASSIGNING <struct>

ASSIGN COMPONENT 'F1' OF STRUCTURE <struct> INTO <fs>.

<fs> = 'X'.

ENDLOOP.

How do we normally test the performance of a program? How can we analyze it in ST05? How could we know that this program performs faster than this one.

Thanks to whoever can answer my questions.

Moderator message: please search for available information (e.g. forum sticky notes) before asking, also compare yourself to find out.

locked by: Thomas Zloch on Sep 12, 2010 9:02 PM