use a file as a database, access rights

[Kartic]

Torsten,

Please explain the environment you are planning to use - Operating
System, whether you have full control of the machine that runs the
database, how many users?.

If you are using Windows and if your needs are simple, you can use
Access as it has some simple access control that  can be setup.

Also, the part about "database would store all its data in a file" is
not very clear. Are you wanting to use a flat-file database and also
have security implemented in it?  If you are on linux/*BSD machine,
consider using a real database.

Fine access control can be implemented in your application (e.g. only
the creator of a record and his/her superiors can edit it, all others
view it)

Please send more details to receive useful recommendations.
Thanks,
--Kartic