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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.
Access methodsThis section describes access methods, explains why you create user-defined access methods, and shows you how to create user-defined access methods
Access-method componentsWhen you add an access method to HCL Informix®, you add, or register, a collection of C user-defined routines (UDRs) in the system catalog. These UDRs take advantage of the Informix® application programming interface (API), the Virtual-Index Interface (VII).
Components that the Informix® database server provides
SQL extensionsThe HCL Informix® extension to ANSI SQL-92 entry-level standard SQL includes statements and keywords that specifically call user-defined access methods.
Specify an access method for a virtual indexThe user needs a way to specify a virtual index in an SQL statement.

Specify an access method for a virtual index

The user needs a way to specify a virtual index in an SQL statement.

To create a virtual index with the CREATE INDEX statement, a user specifies the USING keyword followed by the access-method name and, optionally, with additional access-method-specific keywords.

With the IN clause, the user can place the virtual index in an extspace or sbspace.

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