> what the best optimisation advice can you gave me ?

If data lost are not critical or you have UPS on the server, you can
turn off Forced Writes.

> only 100 000 row in this table. do you think that this stored procedure can be optimized ?

Yes. Your procedure uses the slowest way to do insert-or-update. You
didn't mentioned FB version but modern ones have "INSERT OR UPDATE"
statement while for older ones you can use ideas from here:
http://ibase.ru/devinfo/testiu.htm

SY, SD.