Thank you for the sign in/sign out suggestion. Yes, this is very helpful. On another note, I have solved the issue of disappearing contacts. The source of the lost contacts data is the relationship between a Google internet account in my preferences setting and the relationship between mail, contacts and calendar. Apparently, Google disabled an internet account due to lack of password sign in from a previous employer. When I re-enable this account, all of my missing contacts were restored. HOW these contacts got associated with this account is total mystery to me. I did NOT use SIRI to import these contacts. I entered these contacts by hand on my MacBook Pro laptop. A large number of contacts 'disappeared' from my contact list on my laptop based on this relationship. A total mystery. But am relieved to have all of my data. Thank you.