Category: Troubleshooting

A router for every SQL Server login and permission failure. Find your error number, read the real 18456 state from the ERRORLOG, and go straight to the page that owns the fix.

BULK INSERT fails with 4861 and Access is denied on a file you can open in Notepad. With a SQL Server login the file is opened by the service account, not by you. The reproduction, the operating system error codes that mean something else, and the double hop.

Msg -2 comes from the client library, not from SQL Server. Here is how to tell the execution timeout from the connection timeout, find out whether the query was blocked when the client gave up, and why raising the timeout is not a fix.

Nobody has sysadmin, sa is disabled or its password is gone, and the instance is still running. The supported recovery is single-user mode, and it needs local admin on the box, not a SQL permission.

The backup is from a newer version of SQL Server than the server restoring it, and no option changes that. What the two version numbers mean, why attach fails with 948, and the routes that work.

The same query returns instantly in SSMS and crawls from the application. SSMS connects with ARITHABORT ON and a .NET client connects with it OFF, so the plan cache holds two plans for one query. The query that proves it, and the fixes in order.

Restore chain errors 4305, 4326 and 3159: what the two LSNs in the message mean, which file to apply next, and how to back up the tail of the log before you overwrite anything.

This is the error every patch window can raise and almost nobody plans for. The Cumulative Update installed, the service came back, and now every application login is refused with 18401. Nothing is broken yet. SQL Server is running the second half of the patch, and it will not let anyone in until that half…

Msg 3101 means SQL Server cannot get exclusive access to the database you are restoring. Find the connected sessions, stop clients reconnecting, and retry only when it is safe to disconnect users.

Error 26 means the client could not look up a named instance’s port. Check the instance name, the SQL Server Browser and UDP 1434, or connect with server,port.