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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 syntaxThe database server expects a particular prototype for each purpose function. As the access-method developer, you program the actions of a purpose function but must use the parameters and return values that the Virtual-Index Interface (VII) prototypes specify.

Purpose-function syntax

The database server expects a particular prototype for each purpose function. As the access-method developer, you program the actions of a purpose function but must use the parameters and return values that the Virtual-Index Interface (VII) prototypes specify.

For each purpose function that your access method provides, use the prototype that the topics in this section show, but change the prototype-function name to a unique name. For example, you might save your version of am_open with the name vindex_open(). To associate the unique purpose-function names to the corresponding prototype names, use the CREATE SECONDARY ACCESS_METHOD statement.

The parameter list for each purpose function includes (by reference) one or more descriptor data structures that describe the SQL statement keywords or oncheck options and the specified index that requires the access method.

Purpose functions are entry points from which the access method calls other routines from the access-method library, DataBlade® API functions, and the VII functions that Accessor functions describes.

This section lists purpose-function prototypes in alphabetical order.

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