We had some problems after upgrading to v2.0.8 from v2.0.2 on Windows 2008 R2. (DB: SQL Server Express 2012)
After the upgrade, we would get an error message "the connection timed out" when trying to connect with the NetXMS Console.

After setting DebugLevel in netxmsd.conf to 7 and restarting the NetXMS Core service, the following  error message started appearing in the log:
[16-May-2017 14:49:38.523] [DEBUG] Database Connection Pool exhausted (call from .\config.cpp:344)

I stopped the service, increased DBConnectionPoolMaxSize in the config table of the database from 40 to 100 and restarted it after which the problem appears to be solved.
Posted here for reference for other users and any suggestions.

Server statistics:
Total number of objects: 53241
Number of monitored nodes: 1016
Number of collectable DCIs: 6447