Increasing the number of data sets for an index

By increasing the number of data sets that are used for an index and spreading those data sets across the available I/O paths, you can reduce the physical contention on the index.

Using data-partitioned secondary indexes, or making the piece size of a nonpartitioned index smaller, increases the number of data sets that are used for the index.

A secondary index on a partitioned table space can be partitioned. When you partition an index, the partitioning scheme is that of the data in the underlying table, and each index partition has its own data set. Although data-partitioned secondary indexes promote partition independence and can provide performance advantages, they do not always improve query performance. Before using a data-partitioned secondary index, understand the advantages and disadvantages.