I've recently run down a problem that can cause a hang when you try to execute extremely large networks that involves a deadlock situation in the socket communication between the exec and the UI. To get around it I've added an environment variable that allow you to specify a larger socket buffer size (if the setsockopt call is available), named DX_SOCKET_BUFSIZE. The value assigned to it is passed as the parameter to setsockopt for SOL_SNDBUF and SOL_RCVBUF. I think the default is 32767, and the range is clamped to the max allowed by the system. The value used is clamped to the max allowed by the system; see your sysadmin if you need up this. I'm using 262144.
Greg
