Open Cursor - internal table

Hello,

I'm trying to use the

OPEN CURSOR

statement in my FM which is used for data extraction to split the data in packages of 10 000.

The problem is that I have an internal table where my data is (because I had to extract it first from a cluster table). How is the correct syntax?

 OPEN CURSOR s_cursor FOR SELECT * FOR ALL ENTRIES IN it_tab

does not work.

Or is there any other possibility to split the data into packages?

thanks

Margit