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 when 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 is modified very often,
you can decrease the fill factor to 70% or whatever you think is best.