Maintaining a Sequence Set: The Use of Blocks II
Using blocks, we can thus keep a sequence set in order by key without ever having to sort the entire set of records.
However, there are certain costs associated with this approach:
- A Blocked file takes up more space than an unblocked file because of internal fragmentation.
The order of the records is not necessarily physically sequential throughout the file. The maximum guaranteed extent of physical sequentiality is within a block.