См. BOL (MS SQL):

sysmessages
Contains one row for each system error or warning that can be returned by Microsoft® SQL Server™. SQL Server displays the error description on the user's screen.

Column name Data type Description
error int Unique error number.
severity smallint Severity level of the error.
dlevel smallint For internal use only.
description nvarchar(255) Explanation of the error with placeholders for parameters.
mslangid smallint System message group ID.