I noticed some Failure Audit errors, in the Windows Application event log of the server that my SQL Server runs on, stating:
Event ID: 18456 Login failed for user 'DOMAIN\username'. Reason: Failed to open the explicitly specified database. [CLIENT: <local machine>]
The user mentioned in the errors was in the
sysadmin server role, and I checked that the user had a default database associated with it. The errors recurred every five minutes. Does anyone have any insight into this issue?
The SQL Server service itself and SQL Server Agent run as that account.