Re: elarm - difference between clear and manual clear
"clear" is supposed to be called when the subsystem that raised an alarm clears that alarm. (E.g. there is a process which monitors free disk space, and raises an alarm when there isn't much free space; then when it notices that there is enough free space again, it will clear the alarm by calling "clear").
"manual clear" is supposed to be called when the subsystem that raised the alarm doesn't clear the alarm, but the user knows that the error condition highlighted by the alarm is not present any more. In this case the user can call "manual clear". (Or even better, if your software has a management interface, that can expose a "clear alarm" button, which should then call "manual clear".)