Creating Read-only Databases
From InterBase
Go Up to Creating a Database (Data Definition Guide)
By default, databases are in read-write mode at creation time. Such databases must be on a writable file system even if they are used only for SELECT, because InterBase writes information about transaction states to a data structure in the database file.
You have the option of changing a database to read-only mode. Such databases can reside on read-only file systems. To change the mode of a database to read-only, you can either use gfix (or the equivalent choice in IBConsole), or you can back up the database and restore it in read-only mode. See the Operations Guide for details on how to change the mode of a database using gfix, gbak, or IBConsole.