With the aid of a user-defined secondary access method,
an SQL statement can use one or more indexes.
Further, with the aid of a user-defined secondary access
method, indexes can provide access to the following extended data:
User-defined types
Data inside a smart large object
External data sources
Nonrelational data
In addition, with the aid of a user-defined secondary
access method, an index can contain any of the following key types:
Return values from a user-defined function
Approximate values such as stem words for a full-text search
Attributes of data such as length
Relative position to other data in a hierarchy or area of space
The end user can use SQL to access both HCL Informix® data
and virtual index data. A virtual index requires a user-defined
access method to make the data in the index accessible to Informix. In the
following figure, a single application processes Informix data
and virtual data in an external location and smart-large-object storage.Figure 1: An application using
a secondary access method