In reply to Mustafa:
Modelsim has the capability to log signals in a compressed data format which is extremely efficient. This is recommended over VCD logging since VCD files are text based and not compressed.
Read the Modelsim user manual for more information about logging signals and viewing waves. Since the Modelsim native logging format is optimized for simulation, you can typically log your entire environment with minimal overhead. This can save you the trouble of having to determine ahead of time what you want to log and change it for each test.
Of course, if you have an extremely large environment, you may not want to log every signal, but it works very well for small environments.
