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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.
DataBlade® API Programmer's GuideThe Informix® DataBlade® API Programmer's Guide describes information about the DataBlade® API, the C-language application programming interface (API) provided with HCL Informix®.
Create user-defined routines
Write a user-defined routineThis section outlines some implementation issues for C user-defined routines (UDRs). This section also describes the specific features and tasks of a C UDR.
Virtual processorsTo service multiple client-application SQL requests, the database server uses virtual processors (VPs). The database server breaks the SQL request into distinct tasks, based on the resource that the task requires. Different VP types, called virtual-processor classes (VP classes), service the different kinds of tasks.
Create a well-behaved routine
Define a user-defined VPYou define a new virtual-processor class in the onconfig file with the VPCLASS configuration parameter.

Define a user-defined VP

You define a new virtual-processor class in the onconfig file with the VPCLASS configuration parameter.

The num option specifies the number of virtual processors in a user-defined VP class that the database server starts during its initialization. The class name is not case sensitive, but it must have fewer than 128 characters. If your DataBlade® uses a prefix, such as USR, begin the names of any user-defined VPs with this prefix.

HCL Informix® supports the following types of user-defined VP classes for execution of an ill-behaved C UDR.


Type of user-defined VP class	VPCLASS option
Yielding user-defined VP	None (default type of user-defined VP class)
Nonyielding user-defined VP	noyield
Single-instance user-defined VP (yielding or nonyielding)	num=1

Important: When you edit the onconfig file to create a virtual-processor class, you must add a VPCLASS parameter and remove the SINGLE_CPU_VP parameter. For more information about the onconfig file, see the .

After you add or modify the VPCLASS configuration parameter, restart the database server with the oninit utility (or its equivalent). For more information about how to restart the database server, see your Informix Administrator's Guide. You can add or drop user-defined virtual processors while the database server is online. For more information, see Add and drop VPs.

When you use a class of user-defined virtual processors to run a C UDR, you must ensure that the name of the VP is the same in both of the following locations:

In the VPCLASS parameter in the onconfig file, which defines the VP class
In the CLASS routine modifier of the CREATE FUNCTION or CREATE PROCEDURE statement, which registers the C UDR in the database

For more information, see Assign a C UDR to a user-defined VP class.

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