Some weeks ago I upgraded an SAP netweaver system (double stack). During the deployment the whole upgrade stopped. In the corresponding log files I didn't find any hint what might have caused this error. In SCN and the published SAP notes no information for this problem was available.
Later I restarted the upgrade. Parallel to this upgrade I checked the server node status using jcmon. When the deployment started again in SUM the infomation came up that the upgrade process started the server node. But in jcmon this wasn't happening. This was the error that caused the problem during the earlier upgrade. Here I started the corresponding server node via jcmon. Shortly afterwards the deployment continued and finished successfully.
Please check the status of your server node during an upgrade using jcmon.