The error NS, #149 is seen if you attempt to open the same database with another LNS application but with a different network interface. For instance the LNS Object Browser is a low level utility for opening and manipulating LNS databases. If you have a database open in OpenLNS CT but then try to open the same database with the object browser but in engineered mode you will see this error. Engineered mode means no network interface which to LNS is a different network interface.
The following error is raised from the object browser application:
Failed to enable engineered system: The system is already opened by another client using a different network interface or database directory. (Subsystem: NS, #149).
If you open the database with the same network interface then no error is seen. Note that this is not the same thing as remote LNS client application opening a database on an LNS server where two different network interfaces are used.