I am running Firebird 2.5.0 on Windows for some time on several customer locations. When the client and the server are in the same network the performance is good. It gets difficult when a more complex network structure (eg. Access via VPN) is in place. I see then error 10054 in the firebird.log and the client needs a lot of time to read data form the database.

I can't help you with that, though others on the list may have suggestions.

 

Searching for solutions I understand the the root cause of the error 10054 is on the network level. In the case the current network setup needs to remain unchanged I consider to access the firebird DB via a shared file:

Using Z:\mysharedfolder\mydb.fdb instead of remotehost:myalias

A s far as I have tested it this works also when some clients access via TCP and others via the file.   Are there any known problems or gotchas on that approach?

Yes.  Unless there is a managing Firebird server or a set of cooperating internet servers running on one machine, there's no coordination between client changes.  The database will rapidly become corrupt.  If your tests were read only or single client, you may not have seen corruption.   Continue and you will.  (See previous message.)