Consider a B-tree index on a value that will always increase monotonically, e.g. a column of type IDENTITY. With a conventional B-tree implementation, whenever a node is full, it will be split 50%/50% ...
So, imagine I have a page that I intend to cause to split. USE master ; GO IF DATABASEPROPERTYEX (N'Pages', N'Version') > 0 BEGIN ALTER DATABASE Pages SET SINGLE_USER WITH ROLLBACK IMMEDIATE; ...