Adding a Filegroup in SQL Server

In this post, we’ll demonstrate the process of adding a new filegroup to a database in SQL Server. While many databases function efficiently with a single data/log file, there are scenarios where adding a filegroup proves beneficial.

Filegroups, as outlined in the demo below, serve as a way to group user-defined data files. The example involves creating a new filegroup with two additional data files.

What are Filegroups in SQL Server?

SQL Server typically operates with two types of files: data files (.mdf) and log files (.ldf). Introducing additional data files, known as user-defined (.ndf) data files, is a common practice. Filegroups in SQL Server, on the other hand, are a means of grouping these user-defined data files.

Best Practices for Working with Filegroups

Database Administrators often add new data files to enhance database performance, especially when dealing with multiple databases on an instance. This practice involves splitting data files and distributing data across multiple disk drives. Another instance where adding a new data file is advisable is when configuring Change Data Capture (CDC). For CDC, creating a separate filegroup is considered a best practice.

For more recommendations for working with Filegroups in SQL Server, check out the Mircosoft Documentation: Database Files and Filegroups: Recommendations

Adding a New Filegroup for a Database

The following SQL script illustrates the creation of a Filegroup and the addition of two new data files:

-- Create a test database

USE [sqlDBA];

-- Create test tables & insert rows from system tables
SELECT * INTO dbo.raw_sysdatabases FROM sys.databases;
SELECT * INTO dbo.raw_sysobjects FROM sys.system_objects;

-- Create a filegroup

-- Check filegroups for the current database
SELECT * FROM sys.filegroups;
SQL Server Create Filegroup

We’re using ALTER DATABASE to add a Filegroup to the sqlDBA database. Then, we add the new data files to the Filegroup in the database:

-- Create data files for Filegroup
    NAME = sqldba_data1,
    FILENAME = 'D:\mssql_data\sqldba_data1.ndf',
    SIZE = 500MB,
    NAME = sqldba_data2,
    FILENAME = 'D:\mssql_data\sqldba_data2.ndf',
    SIZE = 500MB,

-- Check files for a database
USE [sqlDBA];
	file_id, type, type_desc, data_space_id, name, 
	physical_name, state, size, max_size, is_percent_growth, growth
FROM sys.database_files;
SQL Server Add Database Files to Database

In the example above we have successfully added 2 new database files to the sqldba database.

For more information on the ALTER DATABASE SQL Command being used, feel free to refer to the MS Docs Examples:
Adding a file to a database
Adding a filegroup with two files to a database

Inspect New Filegroup and Data Files

To view our new database files via GUI, navigate to the “Shrink Databases” option in SQL Server Management Studio (SSMS).

SSMS > Right-Click Database > Tasks > Shrink:

SQL Server Shrink Database Window Showing Database Filegroup

By following this step-by-step guide, you’ve successfully added a filegroup to a database in SQL Server, enhancing your database management capabilities.

Stay tuned for more insightful tips and tutorials!

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