Background

Total Access Analyzer is the world's leading Microsoft Access add-in product and designed to help you create better Microsoft Access solutions through comprehensive documentation and analysis. Total Access Analyzer offers more than 380 Reports, making it the most power documentation and analysis program for Microsoft Access professionals. 

Question

Which tables are being used at a given moment or which users and what type of block is being used?

Answer

We are not aware of a way that Microsoft Access exposes what table locks are currently occurring.

Performance problems may be related to locking but there are also many other things that can contribute to that. 

Our Total Access Analyzer program reviews all the objects in your database to find errors, performance issues and design improvement suggestions.

For linked tables to Access databases, we have a paper on improving performance by maintaining a constant connection:
http://fmsinc.com/microsoftaccess/performance/linkeddatabase.html

To see who's currently connected to a database and log entrants and exits, check out our Total Access Admin program that provides real-time database connections. It does not provide information on what tables they're connected to.