Is it essential to close the board when optimizing the tables?

What happens if you don't? Could the database get corrupted if someone is using the board at the same time?

From what I've heard, corruption is a possibility. However, I've never been able to find anything official on this.

Thanks. I think I may "hack" that out of the admin page. I can always optimize the tables using phpMyAdmin.

I've done it a few times with the boards on, but not being posted to, but most times I shut the boards off. Either way, I've not had any problems from optimizing.