This problem does not affect services.
The HP-UX 11iv2 application server and the storage device were properly connected and services were running properly. After the I/O activity ceased for a period of time, the application server proactively disconnected itself from the storage device. When it needed to access the storage device, the application server set up a connection again. The same symptom occurred on peer vendors' storage devices.
It is concluded that an HP-UX inherent mechanism defect led to an initiator Link Down on the storage device.