The Problem
SQL Agent won’t start on a Windows cluster for a particular instance
The Symptoms
Seen in Windows Application log
Event: 53 Source: SQLAgent$CF3Common Category: Failover
[sqagtres] OnlineThread: Error 6 bringing resource online.
[sqagtres] OnlineThread: ResUtilSetResourceServiceEnvironment failed (status 6)
The Cause
In Cluster Administrator, the SQL Server Agent had lost its dependency upon the SQL server resource for the affected instance.
The Solution
Add the SQL Server dependency, bring SQL Server Agent online in Cluster Administrator