Access _users table in SocialEngine?

i got a (simple?) problem accessing _users table in SocialEngine. To access tables in SE4 i use this:

$table = Engine_Api::_()->getDbTable(tablename,tablegroup);

and this works fine for _user_online (->getDbTable('online','user')) etc. but I don't know how to access _users table (which has not tablegroup prefix).

i tried:

• ->getDbTable('users')
• ->getDbTable('','users')
• ->getDbTable(null,'users')
• ->getDbTable('foo','what_a')

no way.

Engine_Api::_()->getItemTable('user');

I suggest you read SocialEngine factory codes to find out answer to this kind of questions.