I ran 'amdump' to backup multiple hosts.
The process was hung.
It didn't ask for change tape, but no progress.
Running 'amstatus' always show the following.
      ...
dumping         :   1        0k  9903410k (  0.00%) (  0.00%)
dumped          :  23 11569550k 11569424k (100.00%) ( 53.88%)
wait for writing:  23 11569550k 11569424k (100.00%) ( 53.88%)
    ...

In addition, I got the similar problem yesterday:
I ran 'amdump'. The system asked for change tape after while.
I inserted a tape and pressed return, but the process was hung.
There was no tape device activity.
I had to interrupted the process after one hour.

Is any suggestion?

Thanks!

David