If you compile your Flex project for Flash then you cannot store anything local. Flash runs in the browser and browser as well as Flash security doesn't let you have access to the local file system. But you can compile your project for Air to solve your problem. Air has SQL Light built in. So you can use the respective Air classes to create and maintain a local SQL database which you can use for off-line content.

We have been experimenting with this in a project using the ILOG calendar component trying to sync the Notes calendar. As for the SQL databases we succeeded. However, we did not complete the sync part as other projects took over priority.  

I will check the status of the project and see if I can make it available to you.  The problem is that the coding was done by ICT students and documentation of the code is effectively none existent. 

Reading your posting again I realise you would like to access an .NSF file. I'm not sure if you can create COM objects in Flash. If yes, and provided the Notes client is installed locally you could access an .NSF locally. But then again, I believe that would somewhat defeat the purpose.  

Thanks! Your answer is very usefull!

Now i'll be thinking about changing the DB to Sqlite.