What are the correctness rules for verifying fragmentation? How do we verify the correctness of fragmentation?
Correctness rules of fragmentation
- We should not lose data because of fragmentation
- We should not get redundant data because of fragmentation
- Completeness - To ensure that there is no loss of data due to fragmentation. Completeness property ensures this by checking whether all the records which were part of a table (before fragmentation) are found in at least one of the fragments after fragmentation.
- Reconstruction - This rule ensures the ability to re-construct the original table from the fragments that are created. This rule is to check whether the functional dependencies are preserved or not.
- Disjointness - This rule ensures that no record will become a part of two or more different fragments during the fragmentation process.