After the view is started, a .pid file is created under the view storage directory. The pid of its view_server process is stored in the file, so ClearCase can keep track on which view server process is associated with it. After the view_server process is terminated by "cleartool endview -server ", the .pid file will be removed by ClearCase.
However, in certain situatations, the .pid fails to be removed and the view will have problem starting up again. You can safely delete the .pid file and try to start the view again.