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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-Table Interface GuideThe Informix® Virtual-Table Interface Programmer's Guide explains how to create a primary access method with the Virtual-Table Interface (VTI) so that users have a single SQL interface to HCL Informix® tables and to data that does not conform to the storage scheme of HCL Informix®.
Develop an access methodThese topics describe the steps that you take to implement a user-defined access method with the Virtual-Table Interface (VTI).
Write purpose functionsThe Virtual-Table Interface (VTI) specifies the parameters and return values for a limited set of UDRs, called purpose functions, that correspond to one or more SQL statements.
Insert, delete, and update data

Insert, delete, and update data

The following optional purpose functions support the data-manipulation statements shown in the table.


Purpose function	Statement
am_insert	INSERT
am_delete	DELETE
am_update	UPDATE

If you do support insert, delete, and update transactions for data in extspaces, you might need to write and call routines for transaction management from the purpose functions that create transactions. The database server has no mechanism to roll back external data if an error prevents the database server from committing a complete set of transactions to the corresponding virtual table.

If you do not supply functions for am_insert, am_update, or am_delete, or you do not set the appropriate purpose flags, the database server cannot process the corresponding SQL statement and issues an error.

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