Total Size Limit
Microsoft SQL Server 2005 has a row size limitation, so the combined size of all object’s fields (both standard and user-defined) cannot exceed the predefined limit of 8 KB. In Microsoft SQL Server 2008 and 2012, this restriction is relaxed, but creating rows larger than 8 KB might affect performance because SQL Server still maintains a limit of 8 KB per page, i.e. single data access operation.
INFO: For Microsoft SQL Server 2005, see http://blogs.msdn.com/msdnts/archive/2006/12/01/row-size-limitation-in-sql-2000-and-2005.aspx.
INFO: For Microsoft SQL Server 2008, see http://technet.microsoft.com/en-us/library/ms186981%28SQL.105%29.aspx.
INFO: For Microsoft SQL Server 2012, see http://lab.technet.microsoft.com/en-us/library/ms143432%28v=sql.110%29.aspx.
That is why we recommend that you pay attention when adding UDFs (especially of the String type, which are longer than the others). If the total combined size of all fields exceeds the 8 KB limit, you will receive a warning message advising you to reduce the size of the field you are adding or reduce the combined size of all UDFs. If you ignore the advice, data loss will occur.
NOTE: Memo fields have a special structure and don't count against the 8KB limit. These fields only occupy 4 bytes in the record as a reference to the data chunk stored in an external file.