Quick answer: The three most common MSSQL errors each have a clear cause. "Login failed for user" is a credentials or authentication-mode problem. A connection timeout means the server is unreachable - usually TCP/IP or the firewall. A database marked "Suspect" indicates file corruption or a missing log and needs recovery. Here is how to resolve each.
The server was reached but rejected the credentials. Confirm the password, ensure SQL Server authentication mode is enabled (not Windows-only), and check the login is mapped to the database with the right permissions. The error state number in the log narrows the exact cause.
The client could not reach the server at all. Confirm TCP/IP is enabled in SQL Server Configuration Manager, the service is running, the port (usually 1433) is open in the firewall, and you are using the correct address and port.
This signals corruption or a log problem. Do not panic - restore from a recent backup if you have one. If not, set the database to emergency mode, run a consistency check, and repair, ideally with expert help since repair options can risk data. Take a copy of the files first.
What does error 18456 mean?
It is the generic "login failed" error; the accompanying state number identifies whether it is a bad password, disabled login, or wrong auth mode.
How do I prevent suspect databases?
Keep reliable backups, ensure adequate disk space, and avoid abrupt shutdowns that interrupt writes.
On a SoftSys managed Windows VPS our team monitors SQL Server and handles recovery, so these errors are caught and resolved quickly.
