Design table for performance (order - ordervisibility)

Question

I have tables like order, orderitem, etc. and requirements for order visibility:
- One order can be seen by many users
- One user can see many orders
create table order (orderid number, ...);
create table ordervisibility (orderid number, username varchar2(20));
Order size is estimated to be >=500Mio. Application is a data warehouse with reporting.
The relationship order - user will be skewed: some users will be allowed to see many orders while some will only see a small percentage.
How should we design the system for performance?
We think about creating table ordervisibility as index-organized table. Or are there better approaches like partitioning? Or is the approach with tables order na ordervisibility already suboptimal?

Answer 1

<<<What is your 4 digit Oracle version (result of SELECT * FROM V$VERSION)?
The system does not exist yet. Version will be derived from the requirements or most likely the latest version (e.g. 11.2.0.3 EE with partitioning option)
<<<Are you wanting to prevent users from seeing other orders? You said one user can see many orders but are they NOT supposed to see other orders?
Yes, you are right. We want to prevent other users to see orders that do not belong to them.
<<<What determines which orders a user is allowed to see? A state code, a region code?
The user in the OLTP system decides who can see orders (the user creating the order and maybe other users he selects)
<<<Does this database, data and system already exist or is this a new design? Are there any other security mechanisms already in place? Is any of your data currently encrypted?
The system does not exist yet. No other security mechanisms are planned (e.g. encryption).
VPD is considered to implement the visibility (or alternatively views.)