It's worth studying the data model a bit if you haven't. A good place to start is packages/acs-kernel/sql/.
Splitting data among tables may be new to you, but it enables a lot of powerful querying (among other things).
You can do things like query for all objects created in the last few days, e.g.
select object_id from acs_objects where sysdate - creation_date < 3;
(Oracle syntax)
or query for all the different types of objects in the system
select object_type, count(object_type) from acs_objects group by object_type;
Have fun, and feel free to ask more questions, and to visit the openacs IRC chatroom (irc.freenode.net:6667, #openacs channel).
