As a developer who occasionally takes on DBA roles, I often find myself needing to restore client databases to our test servers for testing and development purposes. However, I ran into issues with ad-hoc backups causing log growth and interfering with maintenance plans. That’s when I discovered the COPY_ONLY backup option in SQL Server, which turned out to be a lifesaver.

Before diving into the details of COPY_ONLY backups, it’s important to understand the concept of recovery models in SQL Server. In most production databases, the “Full” recovery model is commonly used. This model ensures data integrity and allows for emergency restarts in case of outages. However, it also has implications for backups.

When a full backup is taken in the Full recovery model, it initiates a log backup chain. Each subsequent log backup is small and quick, allowing for point-in-time restores. However, if no full backups have been taken since the database entered Full recovery, the log portion of the database can grow indefinitely, consuming disk space.

Previously, the solution was to set databases to the “Simple” recovery model, accepting the risk of potential data corruption. However, SQL Server 2005 introduced the COPY_ONLY backup option, which provides a better solution to this problem.

The COPY_ONLY backup option allows you to take a backup without interrupting the existing backup and restore chain. It ensures that the log portion of the database remains lean and prevents unrestrained log growth. This option was initially not included in the backup dialog in SQL Server Management Studio (SSMS) for SQL Server 2005, but it is available as a checkbox in SSMS for SQL Server 2008 and later versions.

To use the COPY_ONLY backup option in SQL Server 2005, you need to write a SQL statement manually. Here’s an example:

BACKUP DATABASE [YourDatabaseName] TO DISK = N'Path\To\BackupFile.bak' WITH COPY_ONLY

In this example, replace [YourDatabaseName] with the name of your database and specify the path to the backup file. The COPY_ONLY parameter is crucial for taking a COPY_ONLY backup.

When it comes to restoring a COPY_ONLY backup, there is a caveat. The restore dialog in SQL Server 2005 SSMS does not understand backups made with the COPY_ONLY option. Therefore, if you script the backup, you must also script the restore. Here’s an example of a restore script:

RESTORE DATABASE [YourDatabaseName] FROM DISK = N'Path\To\BackupFile.bak' WITH REPLACE

In this script, replace [YourDatabaseName] with the name of your database and specify the path to the backup file. The REPLACE parameter allows you to overwrite an existing database on the server if necessary.

It’s important to note that both the BACKUP and RESTORE commands have additional parameters not covered in this brief explanation. Additionally, some databases may have multiple segments, such as separate file groups for tables, views, and stored procedures, or multiple physical files for log segments.

In conclusion, the COPY_ONLY backup option in SQL Server is a valuable tool for taking backups without disrupting the existing backup and restore chain. It helps prevent log growth and ensures efficient database restores. By understanding how to use this option effectively, you can streamline your backup and restore processes and avoid unnecessary complications.