How To Make A FileGroup Read Only in SQL Server 2005

How to make a filegroup read only in SQL Server 2005? This question popped up today on tek-tips. This is how you do that: First we will create a new database named TestFilegroup. Next we will add a filegroup named Test1FG1 which contains a file named test1dat3.
The next step is to do an alter database modift filegroup readonly command
Here is the complete script

USE master
go

--Create New DB For Testing
CREATE DATABASE TestFilegroup
go


--Create FileGroup
ALTER DATABASE TestFilegroup
ADD FILEGROUP Test1FG1;

--Add file to fileGroup
ALTER DATABASE TestFilegroup
ADD FILE
(
NAME = test1dat3,
FILENAME = 'c:\t1dat3.ndf',
SIZE = 5MB,
MAXSIZE = 100MB,
FILEGROWTH = 5MB

)
TO FILEGROUP Test1FG1

--Make FileGroup ReadOnly
ALTER DATABASE TestFilegroup
MODIFY FILEGROUP Test1FG1 Read_Only;

Use Read_Only not ReadOnly because the keyword READONLY will be removed in a future version of Microsoft SQL Server. Avoid using READONLY in new development work, and plan to modify applications that currently use READONLY. Use READ_ONLY instead.




Now what happens when you try to create a table on filegroup Test1FG1?
USE TestFilegroup
GO
CREATE TABLE abc (id INT) ON Test1FG1

You will see the following error message
Server: Msg 1924, Level 16, State 2, Line 1
Filegroup 'Test1FG1' is read-only.

You can use sys.filegroups and check the is_read_only column to find out if a filegroup is read only
SELECT is_read_only
FROM sys.filegroups
WHERE name = 'Test1FG1'

Here is the result
is_read_only
------------
1




Using NTFS Compression with Read-Only User-defined Filegroups and Read-Only Databases
SQL Server 2005 supports NTFS compression of read-only user-defined filegroups and read-only databases. You should consider compressing read-only data in the following situations:
You have a large volume of static or historical data that must be available for limited read-only access.
You have limited disk space.