CommVault Agent Setup
From Tranzman Documentation
CommVault Specifics
The agent must run as a user that has permissions to connect to SQL Server. By default, the installation configures it as a "Local Service", which does not have the necessary permissions.
You must change the user login used by the service to a suitable account. To do this, open services and find tranzman in the list.
Right-click and select properties. In the window that appears, select the "Log-on" tab.
Select "This account" and enter the username and password of the account to use, then click OK.
Finally, restart the service.