Veeam backup job warning – Unable to truncate Microsoft SQL Server transaction logs

I have created a new backup job in Veeam Backup & Replication that contains a VM running Microsoft SQL server.  I have enabled application-aware processing.  However, the job completes with the following warning:

Unable to truncate Microsoft SQL Server transaction logs. Details: Failed to process ‘TruncateSQLLog’ command. Failed to truncate SQL server transaction logs for instances: SHAREPOINT. See guest helper log.

Having reviewed the guest helper log, which is stored in C:\ProgramData\Veeam\Backup on the VM, it is clear that the service account used by the backup job does not have access to the SQL databases:

INFO        RPC: truncation SQL logs.
Job UID: '{759cbd3e-efca-4ca3-b0cc-611954bc864f}'.
Login: webbworld\veeam_serv
Enumerating SQL instances
Enumerating Microsoft SQL Server instances by service names.
SQL instance found: [SHAREPOINT]
Enumerating Microsoft SQL Server instances by service names.. Ok.
Truncating database logs (SQL instance: SHAREPOINT). User: webbworld\veeam_serv.
Using default SQL provider 'sqloledb' to connect to SQL server
INFO                            Connecting to mssql, connection string: Provider='sqloledb';Data Source='(local)\SHAREPOINT';Integrated Security='SSPI';Persist Security Info=False, timeout: 15
Code = 0x80040e4d
Code meaning = IDispatch error #3149
Source = Microsoft OLE DB Provider for SQL Server
Description = Login failed for user 'WEBBWORLD\Veeam_Serv'.
COM error:  Code: 0x80040e4d

The solution was to grant the service account used by the backup job ‘DB_BackupOperator’ rights on each of the databases being backed up.  Now the job completes successfully.