Found below tips on the help.chm, will try this:
Troubleshooting Networking and Communication
You can configure the TCP/IP protocol to use 8 instead of the default 5 retransmissions. It is better not to use higher values because each increment doubles the timeout. The setting applies to all network connections, not only to connections used by Data Protector.
If the Cell Manager is running on a Windows system, apply the change on the Cell Manager system first. If the problem persists or if the Cell Manager is running on a UNIX system, apply the change to the problematic Windows clients.
Add the DWORD parameter TcpMaxDataRetransmissions and set its value to 0x00000008(8) under the following registry key:
Restart the system.
KeepAlive Parameters also work with DP6.xx
Suggest to set these in omnirc-File on the Client and to restart DP Inet.