Essentially, all Application backups, such as SQL have their own Backup method. The 'sql_bar' is the way that DP connects to these methods and provides the media management and reporting for the backup. In the Integration Guide
Data Protector integrates with SQL Server through the Data Protector sql_bar.exe executable,
installed on SQL Server. It implements multiple virtual devices for backup and restore and transforms
SQL Server Virtual Device Interface (VDI) commands from SQL Server into Data Protector backup
or restore streams.
The VDI architecture allows the Data Protector General Media Agent to access data directly in the
SQL Server memory, provided the devices are directly attached to SQL Server. Therefore, high
backup and restore speed is achieved.
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When you go into the Users context in the GUI, and right-click on any server, pick 'Add Component', and choose MS_SQL, DP will install any necessary files on that server, including 'sql_bar'
Then,
An SQL Server instance is configured during the creation of the first backup specification. The
configuration consists of setting the user account that Data Protector should use to connect to the
SQL Server instance. The specified login information is saved to the Data Protector SQL Server
instance configuration file on the Cell Manager.
This is done either using the GUI, or from the MS-DOS prompt on the SQL server
sql_bar config [-appsrv:SQLServerClient] [-instance:InstanceName]
[-dbuser:SQLServerUser -password:password]
-appsrv:
SQLServerClient
The client system on which the SQL Server instance is running. This option is not required if
you run the command locally
-instance:
InstanceName
The SQL Server instance name. If you omit this option, the default SQL Server instance is
configured
-dbuser:
SQLServerUser -password:password
The SQL Server user account (SQL Server authentication)
-dbuser:
WindowsUser -password:password -domain:domain
The Windows domain user account (Windows authentication)
All of this is in the Microsoft Products integration guide