In DB2, what is the difference between a clustered index and a non-clustered index?

A clustered index physically reorders the rows in the table based on the index key, which means the rows are stored on disk in the same order as the index. This speeds up retrieval of data based on that index key but may slow down inserts and updates because the rows must be physically reordered. A non-clustered index does not change the physical order of the data on disk and thus doesn't affect insert or update performance, but may be slower for retrieval operations.