PVM provides notification messages as a means to implement fault recovery in an application. A task can request that the system send a message on one of the following three events:
Type Meaning ----------------------------------------------- PvmTaskExit Task exits or crashes PvmHostDelete Host is deleted or crashes PvmHostAdd New hosts are added to the VM -----------------------------------------------
Notify requests are stored in the pvmds, attached to objects they monitor. Requests for remote events (occurring on a different host than the requester) are kept on both hosts. The remote pvmd sends the message if the event occurs, while the local one sends the message if the remote host goes down. The assumption is that a local pvmd can be trusted; if it goes down, tasks running under it won't be able to do anything, so they don't need to be notified.