The following are the flags that you may want to use at database open time. Note that this list is not exhaustive — it includes only those flags likely to be of interest for introductory, single-threaded database applications. For a complete list of the flags available to you, see the Berkeley DB C API guide.
To specify more than one flag on the call to DB->open(), you must bitwise inclusively OR them together:
u_int32_t open_flags = DB_CREATE | DB_EXCL;
DB_CREATE
If the database does not currently exist, create it. By default, the database open fails if the database does not already exist.
DB_EXCL
Exclusive database creation. Causes the database open to fail if the database already exists. This flag is only meaningful when used with DB_CREATE.
DB_RDONLY
Open the database for read operations only. Causes any subsequent database write operations to fail.
DB_TRUNCATE
Physically truncate (empty) the on-disk file that contains the database. Causes DB to delete all databases physically contained in that file.