Data access methods

Data access methods are used to process queries and access data.

In general, the query engine has two kinds of raw material with which to satisfy a query request:

• The database objects that contain the data to be queried
• The executable instructions or operations to retrieve and transform the data into usable information

There are only two types of permanent database objects that can be used as source material for a query — tables and indexes. Indexes include binary radix and encoded vector indexes.

In addition, the query engine might need to create temporary objects to hold interim results or references during the execution of an access plan. The DB2® Symmetric Multiprocessing feature provides the optimizer with additional methods for retrieving data that include parallel processing. Finally, the optimizer uses certain methods to manipulate these objects.