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Extending Informix®Beyond standard relational database objects, HCL Informix® can be extended to handle specialized data types, access methods, routines, and other objects. Informix® includes many built-in extensions that are fully integrated in the database server. Informix® also provides DataBlade® modules, which are packages of extended database objects for a particular purpose and that are installed separately from the database server. Alternatively, you can create your own user-defined objects for Informix®.
Creating extensionsYou can create user-defined data types, routines, access methods, and other database objects to suit your needs. You can use application programming interfaces to write user-defined routines and applications that access data in Informix® databases.
Virtual-Index Interface GuideThe Informix® Virtual-Index Interface Programmer's Guide explains how to create a secondary access method with the Virtual-Index Interface (VII) to extend the built-in indexing schemes of HCL Informix® typically with a DataBlade® module.
Purpose-function referenceThese topics describe the purpose functions that the access-method developer provides.
Purpose-function flowThe diagrams in this section show, for each SQL statement, which purpose functions the database server executes. Use the diagrams to determine which purpose functions to implement in the access method.

Purpose-function flow

The diagrams in this section show, for each SQL statement, which purpose functions the database server executes. Use the diagrams to determine which purpose functions to implement in the access method.

The complexity of the purpose-function flow for each statement determines the order in which the statement appears in this section.

This section also describes the oncheck utility interface.

Tip: The database server invokes the am_open and am_close purpose functions once per fragment for the first SQL statement that references a new virtual index. After the initial calls to am_open and am_close, the database server resumes the normal purpose function flow for the active SQL statement.

The following statements result in an additional call to am_open and am_close before the INSERT statement:

CREATE TABLE newtab (...) USING myvti
INSERT INTO newtab VALUES (....)

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