Creating an index strategy

Db2 for i provides two basic means for accessing tables: a table scan and an index-based retrieval. Index-based retrieval is typically more efficient than table scan when less than 20% of the table rows are selected.

There are two kinds of persistent indexes: binary radix tree indexes, which have been available since 1988, and encoded vector indexes (EVIs). Both types of indexes are useful in improving performance for certain kinds of queries.