BFILE Data Type

The BFILE data type in Oracle is used to store binary file data that resides in the operating system’s file system, rather than within the database itself. It is an important feature when you need to store and access large binary files (such as images, videos, PDFs, etc.) externally but still need to reference them in the Oracle database.

 

1. What is BFILE?

The BFILE data type is designed to store a pointer to a binary file that exists outside the Oracle database, typically in the file system of the operating system. This type does not store the actual file data inside the database; it only stores the file path to access the file on the disk.

In simple terms:

• BFILE allows you to reference external files (binary files) that reside outside the Oracle database, but you can interact with them as if they were part of the database.

 

2. Key Characteristics of BFILE

• External File Storage: Unlike other LOB types (CLOB, BLOB), BFILE data is stored outside the Oracle database. Only a reference (file path) to the external file is stored within the database.
• Max Size: The maximum size of a BFILE is 4 GB (same as other LOB types).
• Read-Only: A BFILE is read-only. You cannot directly modify the binary content stored in the external file using SQL. You can, however, read it using various functions.
• External Files: Typically, BFILEs store large binary files (e.g., images, audio, video, documents) that are stored in the operating system file system, not in the database.
• File System Location: The BFILE stores a reference to an external file’s location using a directory object.

 

3. Defining a BFILE Column

You can define a BFILE column in a table using the following SQL syntax:

CREATE TABLE documents (

    doc_id NUMBER PRIMARY KEY,

    doc_file BFILE

);

In this example, the doc_file column is of type BFILE, meaning it will store a reference to the binary file located outside the database.

 

4. Working with BFILE in Oracle

4.1. Creating a Directory Object

Before working with BFILEs, you must create a directory object in Oracle, which refers to the location in the file system where the binary files are stored.

CREATE DIRECTORY bfile_dir AS '/path/to/your/files';

This creates a directory object named bfile_dir, which points to a specific file system path.

4.2. Granting Permissions

You also need to grant appropriate permissions to the user for accessing the directory:

GRANT READ ON DIRECTORY bfile_dir TO your_user;

 

4.3. Inserting a BFILE

To insert a BFILE reference into the table, use the BFILENAME function, which takes the directory object name and the filename as parameters:

INSERT INTO documents (doc_id, doc_file)

VALUES (1, BFILENAME('BFILE_DIR', 'example.pdf'));

In this example, the BFILENAME function returns a BFILE reference to the example.pdf file stored in the BFILE_DIR directory.

4.4. Selecting a BFILE

To retrieve the BFILE reference from the table, you can use a SELECT query:

SELECT doc_file

FROM documents

WHERE doc_id = 1;

This will return the BFILE reference (the file location and name) stored in the doc_file column.

 

5. Accessing the Contents of a BFILE

To access the contents of a BFILE, you can use the DBMS_LOB package. For example:

·        Reading BFILE Data:

DECLARE

    bfile_locator BFILE;

    file_content VARCHAR2(100);

BEGIN

    -- Get the BFILE reference

    SELECT doc_file INTO bfile_locator FROM documents WHERE doc_id = 1;

    -- Read the first 100 bytes of the BFILE

    DBMS_LOB.OPEN(bfile_locator, DBMS_LOB.LOB_READONLY);

    DBMS_LOB.READ(bfile_locator, 100, 1, file_content);

    DBMS_LOB.CLOSE(bfile_locator);

    -- Output the first 100 bytes

    DBMS_OUTPUT.PUT_LINE(file_content);

END;

In this example, the DBMS_LOB.READ function reads the first 100 bytes of the BFILE and stores it in a variable.

 

6. Updating BFILE Data

You cannot directly modify the content of a BFILE since it is read-only. However, if you need to replace the file, you can update the BFILE reference (the file path) by using the BFILENAME function again.

For example:

UPDATE documents

SET doc_file = BFILENAME('BFILE_DIR', 'new_example.pdf')

WHERE doc_id = 1;

This replaces the old BFILE reference with a new one pointing to a different file.

 

7. Deleting BFILEs

Since BFILE is just a reference to an external file, deleting the BFILE from the database only removes the reference. The actual file in the operating system is not deleted. To remove the file from the operating system, you need to use external file system tools.

DELETE FROM documents

WHERE doc_id = 1;

 

8. Performance Considerations

• BFILE is external to the database: As the binary file data is not stored in the database, it does not take up space in the database itself. However, it can still impact performance if the external file is large or accessed frequently.
• File System Access: Since BFILE relies on the file system, accessing files may be slower if the files are stored on network drives or if the file system is under heavy load.
• Read-Only Nature: BFILE objects are read-only, so if you need to perform modifications to the content, you need to manage that outside Oracle (e.g., via an external tool or script).

 

9. Directory Objects and Security

• Directory Objects: BFILE data requires a directory object in Oracle. The directory object must point to a directory on the server where the files are stored.
• Security Considerations: Only users with appropriate privileges (i.e., READ privilege) can access BFILE data. If you need to provide write access to external files, you would need additional administrative setup, and the BFILE itself cannot be updated directly.

 

10. Use Cases for BFILE

Some common scenarios for using BFILE include:

• Multimedia Files: Store images, audio, or video files externally while keeping metadata (such as file names) in the database.
• Documents: Store large documents such as PDF files, Word documents, or spreadsheets outside the database.
• Scientific Data: Handle large data files that are too large to store inside the database but need to be referenced by the database application.
• Logs and Binary Data: Store large binary log files or other types of binary data in external locations.

 

11. BFILE vs. BLOB

• BFILE stores references to binary files on the file system, while BLOB stores binary data directly inside the database.
• BFILE is used when you need to manage large files externally (outside the database) while still referencing them from within Oracle.
• BLOB is ideal when you need to store binary data completely within the database itself.

 

12. Best Practices

• Storage Management: When using BFILE, ensure that the external file system is well-managed and regularly backed up.
• File Organization: Maintain a consistent file naming and directory structure to ensure easy management of BFILE references.
• Access Control: Control access to external files by carefully managing directory permissions to avoid unauthorized access to sensitive files.

 

Conclusion

The BFILE data type in Oracle is a powerful feature that allows you to store and manage large binary files externally while still making them accessible from within the Oracle database. It is ideal for situations where the binary data is too large to store in the database but must still be referenced by database applications. By understanding its usage, limitations, and best practices, you can effectively manage external binary files in your Oracle environment.