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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.
Develop an access methodThese topics describe the steps that you take to implement a user-defined access method with the Virtual-Index Interface (VII).
Write purpose functions
Create and drop database objects

Create and drop database objects

In response to a CREATE INDEX statement, the database server executes the function that you register for am_create. If the database server does not find a function name associated with am_create, it updates the appropriate system catalog tables to reflect the attributes of the table that CREATE INDEX specifies.

The am_insert purpose function also pertains to CREATE INDEX. The database server scans the index to read key values and then passes each key value to am_insert.

If you supply a function for am_create, consider the necessity of also providing a function to drop a table that the access method creates. The database server executes the function that you register for am_drop in response to a DROP INDEX or DROP DATABASE statement. If you do not provide a function to drop a virtual index, the database server deletes any system catalog information that describes the dropped object.

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