With regard to collisions a lock of type O behaves like a shared lock (S). This means, it collides with E and X locks (see Lock Collisions).
If an exclusive lock belonging to another owner exists, the optimistic lock cannot be set. It is irrelevant whether the exclusive lock is a conventional E lock or a converted optimistic lock.
An existing optimistic lock also prevents other owners from receiving an E or an X lock directly.
Optimistic locks belonging to different owners are compatible with one another. The first owner who tries to convert an optimistic lock into an exclusive lock can do so successfully (provided no other “normal” shared locks are set). The other optimistic locks become invalidated (deleted from the lock table). If you try to change them, the exclusive lock cannot be set.