The ‘fill factor’ option specifies how full SQL Server will make each index page. When there is no free space to insert new row on the index page, SQL Server will create new index page and transfer some rows from the previous page to the new one. This operation is called page splits.
You can reduce the number of page splits by setting the appropriate fill factor option to reserve free space on each index page. The fill factor is a value from 1 through 100 that specifies the percentage of the index page to be left empty. The default value for fill factor is 0. It is treated similarly to a fill factor value of 100, the difference in that SQL Server leaves some space within the upper level of the index tree for FILLFACTOR = 0.
The fill factor percentage is used only at the time the index is created. If the table contains read-only data (or data that very rarely changed), you can set the ‘fill factor’ option to 100. When the table’s data modified very often, you can decrease the ‘fill factor’ option to 70 percent, for example.
Having explained page splits in detail I would warn you in over looking at this point because more free space means that SQL Server has to traverse through more pages to get the same amount of data. Hence try to strike a balance and arrive at an appropriate value.
