What is a page split?

A page split can occur when SQL Server needs to insert or enlarge a row on an index page that does not have enough free space. SQL Server may allocate another page and redistribute rows between pages.

Frequent page splits can increase logging, I/O, fragmentation, and write cost. Random inserts into the middle of a heavily populated index are a common cause.

Possible responses include choosing a more suitable key, reviewing fill factor, reducing row width, and measuring whether splits are actually a material workload problem.