To backup Microsoft SQL Server, the account used for VM-side processing (application aware processing) requires certain permissions. Veeam recommends assigning the sysadmin role on the SQL Server but it is also possible to assign minimal permissions on the databases it needs to backup, which is the preferred method for security hardening.

The User Guide for VMware vSphere outlines the required permissions as well but for convenience, I've listed them here as well.

Instance-level roles:

Assign these roles:public


Database-level roles:

Assign these roles:

System databases master and model:db_backupoperator



System database msdb:db_backupoperator

db_dat  ...