Machines+People uses the SQLite database. It's an open source database used in many popular applications and millions of users worldwide. It is a single user database that is embedded into applications such as email programs. It is encrypted using AES 128 encryption.

Each organization for which you gather data will have it's own database file. How you store, access, and share these files will depend on your unique needs. If you are a single consultant you might carry them around on a single USB drive. If you are in an organization with several IT consultants you might share them off a server of somekind.

It's very important to back these up from the thumbdrive. If you lose the thumbdrive then you've lost a lot of critical data.