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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 single-instance user-defined VP classTo define a single-instance user-defined VP, specify a value of one for the num option of the VPCLASS configuration parameter.

Define a single-instance user-defined VP class

To define a single-instance user-defined VP, specify a value of one for the num option of the VPCLASS configuration parameter.

The following code fragment creates a yielding single-instance user-defined VP class, single_vp.

VPCLASS single_vp, num=1                # Single-instance VP class

At run time you can determine whether the VP on which a UDR is running is part of a single-instance user-defined VP class with the mi_vpinfo_vpid() and mi_class_numvp() functions. For more information, see Obtain VP-environment information.

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