Contacts File to Backup?

One of the great failing of Outlook is losing Contact and not able to back them up when in their .ost file.
Where are the contacts stored in eM and will they be included in a daily system backup?  Thank you!

They are stored within a SQL database and will be backed up using eM Client’s own automatic backup system if that is enabled. You can also manually do the backup using Menu > File > Backup, or save them using Save As or export, either individually or as a single vCard file for your entire contacts.

External backup applications will not backup eM Client data unless eM Client is closed during the backup.

thank you.  thats very helpful,  Cindy