To monitor an Amazon RDS instance using SQL Diagnostic Manager, create an SQL Server user on the instance with the following minimum permissions.

Complete this task by following the steps below:

1. Right-click the created user from the Logins node located in the Security node of the server in SSMS. 
2. Select Properties and configure the following tabs in the Login Properties Wizard as suggested.

Server Roles

Grant the following server-wide security privileges to the user.

• public
• processadmin
• setupadmin

User Mapping

Select the following databases, review them, and assign them the mentioned role membership as suggested.

•  public role membership to the tempdb database
•  db_datareader role membership to the msdb database
• sysadmin role membership to all monitored databases

Securables

Verify that the following permissions are granted to your server.

• Alter any connection
• Alter any linked server
• Alter any login
• Alter any server role
• Alter server state
• Alter trace
• Connect SQL
• Create any database
• Create server role
• View any database
• View any definition
• View server state