from how i understood it, if this is your first time to go home, you could only process your owwa membership from here in qatar. for the oec certificate, you'll have that done in the philippines at the poea in ortigas. i would suggest that you go to poea early in the morning because the queue could get reeeaaally long. you'll present the oec at the airport on your flight back to qatar.

for those who have gone home before, the oec certificate can be renewed here in qatar.