Read privileges on the directory where the BFILE is located are required to use this property. The operating system-specific permissions must have been set for the directory to make sure that the user can read the directory.
Appropriate privileges must be set up in the database previously. For example, to ensure that a user (scott) can read a directory (BfileDirectory) through the Exists property, the following SQL statement must be executed:
GRANT READ ON DIRECTORY BfileDirectory TO scott;