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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

Avoid database server exceptions

When an SQL statement involves the access method, the database server checks the purpose settings in the sysams system catalog table to determine whether the access method supports the statement and the keywords within that statement.

The database server issues an exception and an error message if the purpose settings indicate that the access method does not support a requested SQL statement or keyword. If a user inadvertently specifies a feature that the access-method design purposely omits and the SQL syntax conforms to the Informix® Guide to SQL: Syntax, the documentation does not provide a solution.

Specify access-method support for statements, keywords, and storage space types in the sysams system catalog table with a CREATE SECONDARY ACCESS_METHOD or Alter ACCESS_METHOD statement.

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