Today we continue our Question of the Day series with question number three.  In case you are just joining us, we are doing a question a day as an exercise in SQL Learning.

What is fill factor?

My first response to this question in normal day-to-day conversation is that fill factor is a great SQL guy that I follow on twitter.   All joking aside, fill factor is an option that will determine how full to create each index page.  In other words, when the index page is filling up and does not have enough room to insert a new row, then SQL Server will generate a new index page and move some of the rows from the last index page to this new page.  This is known as a page split.  If we use the fill factor option, then the server will reserve a set amount of space on each index page and thus will reduce the number of page splits.  The default value for fill factor is 0.

Enjoy!