Inserting a record near the start of a large file could be very time-consuming.
One solution is to create a temporary unsorted file, called an overflow (or
transaction) file. Insertions are added to the overflow file, and periodically, the overflow
file is merged with the main sorted file. This makes insertions very efficient,
but has a detrimental effect on retrievals. If the record is not found during the
binary search, the overflow file has to be searched linearly. Inversely, to delete a
record we must reorganize the records to remove the now free slot