Data and log files are initialized to overwrite any existing data left on the disk from previously deleted files. Data and log files are first initialized by filling the files with zeros when you perform one of the following operations:

• Create a database.

• Add files, log or data, to an existing database.

• Increase the size of an existing file (including autogrow operations).

• Restore a database or file group.

• File initialization causes these operations to take longer. However, when data is written to the files for the first time, the operating system does not have to fill the files with zeros.

Instant file initialization is only available if the SQL Server (MSSQLSERVER) service account has been granted SE_MANAGE_VOLUME_NAME. Members of the Windows Administrator group have this right and can grant it to other users by adding them to the Perform Volume Maintenance Tasks security policy.