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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 extensions
You 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.
User-Defined Routines and Data Types Developer's Guide
The Informix® User-Defined Routines and Data Types Developer's Guide describes how to define new data types and enable user-defined routines (UDRs) to extend HCL Informix.
Improve UDR performance
A virtual-processor class
Using virtual processors with UDRs written in C

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.
- Informix® extensions and DataBlade® modules
  These topics describe how to use built-in database extensions and separately installed DataBlade® modules.
- Creating extensions
  You 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 Guide
    The Informix® DataBlade® API Programmer's Guide describes information about the DataBlade API, the C-language application programming interface (API) provided with HCL Informix.
  - DataBlade® API Function Reference
    The Informix® DataBlade® API Function Reference describes the DataBlade API functions and the subset of Informix ESQL/C functions that the DataBlade API supports.
  - DataBlade® Developers Kit
    The DataBlade® Developers Kit (DBDK) guides contain information about the tools you can use to develop and package DataBlade modules, which extend the functionality of HCL Informix® databases.
  - J/Foundation Developer's Guide
    The J/Foundation Developer's Guide describes how to write user-defined routines (UDRs) in the Java™ programming language for Informix®.
  - R-Tree Index User's Guide
    The Informix® R-Tree Index User's Guide describes the HCL Informix R-tree secondary access method and how to access and use its components.
  - User-Defined Routines and Data Types Developer's Guide
    The Informix® User-Defined Routines and Data Types Developer's Guide describes how to define new data types and enable user-defined routines (UDRs) to extend HCL Informix.
  - Virtual-Table Interface Guide
    The 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.
  - Virtual-Index Interface Guide
    The 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.

Using virtual processors with UDRs written in C

About this task

To run in the CPU VP class, a C UDR must be well behaved; that is, it must adhere to special programming requirements. Running in a user-defined VP relaxes some, but not all, of the programming requirements of a well-behaved routine. For example, these routines can issue direct file-system calls that block further processing by the virtual processor until the I/O is complete. Because virtual processors are not CPU virtual processors, however, the normal processing of user queries is not affected. However, they still cannot perform local resource allocations because they might migrate among the VPs.

To assign a C UDR to a user-defined VP class:

Procedure

When you register an external function or procedure, assign it to a class of virtual processors with the CLASS routine modifier of the CREATE FUNCTION or CREATE PROCEDURE statement.
The CLASS routine modifier specifies the virtual-processor class with the following syntax:
```
CLASS = vpclass_name
```
In this syntax, vpclass_name is the name of the user-defined VP class that you have configured in the database server. The class name is not case sensitive.
Configure new user-defined virtual-processor classes in the onconfig file with the VPCLASS configuration parameter.
The following sample onconfig entry creates the user-defined VP class newvp:
```
VPCLASS newvp,num=3                      # New VP class for testing
```
The num option specifies the number of virtual processors that the database server starts. For the newvp virtual-processor class, the database server initially starts three virtual processors.

Results

The VP class need not exist when the routine is registered. However, when you execute the routine, the class must exist and have virtual processors assigned to it. If the class does not have any virtual processors, you receive an SQL error.

For more information about how to choose a virtual-processor class for a C UDR, see the Informix® DataBlade® API Programmer's Guide. For information about the VPCLASS configuration parameter, see the Informix® Administrator's Reference.