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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.
Design decisionsThese topics present the choices that you make to optimize the performance and flexibility of the access method that you can create with the virtual-index interface (VII).
Supply error messages and a user guide for your functionsPlan the user-guide and error messages for the access-method purpose functions that you are providing.
Avoid database server exceptions
SQL restrictionsThe database server raises exceptions due to restrictions that the virtual-index interface (VII) imposes on SQL.

SQL restrictions

The database server raises exceptions due to restrictions that the virtual-index interface (VII) imposes on SQL.

A user cannot specify a dbspace in a CREATE INDEX or ALTER FRAGMENT statement. The VII does not support the following statements for virtual indexes:

An ALTER INDEX statement that adds, drops, or modifies a column
A LOCK TABLE or UNLOCK TABLE statement
An ATTACH or DETACH keyword in an ALTER FRAGMENT statement

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