Accessing a Vdb on a locked volume - addendum

[Giulio]

following my post about trying to acces a valentina DB from an 
REALBasic app having both burned on a CD or DVD, I've found a on the 
documentation a db property called isreadonly:

"Returns TRUE if this database is read only, i.e. it is located on the 
locked volume or files  of databases are marked as read only."

So can I assume that a db can be opened only for read from a burned 
support, right?

But then how can I avoid to have an exception opening such a db?

Thank you,

        Giulio