Hi Dirk,
Talking specifically about the embedded version (not client-server)…the help says:
Client access can be only via the local (XNET) protocol, i.e. NOT a TCP/IP local loopback connection string that includes the server name “localhost” or the IP address 127.0.0.1. The embedded server supports only the local connect to an absolute database file path without a server name.
The client program gets exclusive access to the database file after successful connect. If another Firebird server already has a client attached to the database, the client program will be denied access. This is intentional.
Compare that to SQLite, where the client program does not get exclusive access to the file, so you can have multiple clients happily retrieving information from the same SQLite database concurrently. Changing data is another story.
Jon