Local permissions for NetBackup user on SQL Server

Hi everybody,

I was wondering if there is an official document or some documentation about why is necessary that a domain user created to backup SQL Server with NetBackup needs to be in the local administrator group? We're not using Local System so we created this user but need to have some evidence to our security team to get this kind of permission. I have only found the tech notes about SQL Server permissions but not about Windows server permissions for example.

Any help is welcome.

Thank you!!