1, access is a typical database does not need special environment, because windows has built-in driver access program, so in the windows environment can directly call asp to access access. access as a small desktop database, in terms of functionality and performance of course, there is a lack of, but I do not know what you mean by security! But I'm not sure what aspect of security you're referring to, is it the ability to be downloaded directly by HTTP? There are ways to prevent that. access's main limitations are the lack of stored procedures and triggers, and the fact that it's not suitable for large data volumes.

2, db file may be paradox database, this is a kind of now few people no longer use the small database, do not recommend that you learn. As for the .dat file is even more rare, it is possible to export the database file or custom data format.

3, currently placed in the local direct use, the most convenient is access.

4, oracle is a very powerful database, but to be proficient in oracle is a very difficult thing. If you just write some simple system, do not recommend that you use this.

5, for your current state, basically access and mssql is the most suitable.