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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
Storage spaces and fragmentation

Storage spaces and fragmentation

An SQL statement fails if it specifies a storage space that does not agree with the am_sptype purpose value in the sysams system catalog table. In the user guide, specify whether the access method supports sbspaces, extspaces, or both. Advise the user how to do the following:

Create sbspace or extspace names with the onspaces command
Specify a default sbspace if the access method supports sbspaces
Locate the default extspace if the access method creates one
Specify an IN clause in a CREATE INDEX or ALTER FRAGMENT statement

If the access method supports fragmentation in sbspaces, advise the user to create multiple sbspaces with onspaces before issuing an SQL statement that creates fragments.

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