A hung daemon is detected by the archive_supervisor because its logfile is no longer updated. Hung daemon are usually due to device problems. The logfile should give an idea about which command is actually hung. A look at the tail of the file /var/adm/messages which logs the console messages might also be informative.
The daemon must then be killed manually with the kill pid Unix command. The daemon's pid can be found either in the .pid file of its working directory or in the ps -ax list.
Once the problem is fixed, the daemon should be restarted as explained in 6.1.2 as of course it couldn't possibly die gracefully.