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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.
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®.
Concepts
This section introduces the infrastructure for creating and executing user-defined routines (UDRs) and applications that you write in Java™ to run in the HCL Informix® database server.
Java™ virtual processors
Java™ UDRs execute on specialized virtual processors called Java virtual processors (JVPs). A Java Virtual Machine (JVM) is embedded in the code of each JVP.

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®.
    - Concepts
      This section introduces the infrastructure for creating and executing user-defined routines (UDRs) and applications that you write in Java™ to run in the HCL Informix® database server.
      - Features of Java™ user-defined routines
      - Java™ virtual processors
        Java™ UDRs execute on specialized virtual processors called Java virtual processors (JVPs). A Java Virtual Machine (JVM) is embedded in the code of each JVP.
      - System catalog tables
        The sysroutinelangs, syslangauth, and sysprocedures system catalog tables contain information about the UDRs written in Java™ code.
    - Prepare for Java™ support
      You must install and configure software before you can write user-defined routines (UDRs) in Java™ code.
    - Configuration parameters
      This section documents the configuration parameters that you need to set to use UDRs written in Java™ code. Set these parameters in the database server configuration file (the onconfig file).
    - Create Java™ user-defined routines
      A user-defined routine (UDR) is a routine that an SQL statement or another UDR can invoke. UDRs written in Java™ code use the server-side implementation of the Informix® JDBC Driver to communicate with the database server.
    - The Informix® JDBC Driver
      All UDRs written in Java™ code can access the database server data through the Informix® JDBC Driver application programming interface (API). This section briefly describes the Informix implementation of the Informix JDBC Driver API and the server-side Informix JDBC Driver.
    - Opaque user-defined data types
      This section describes how to use opaque user-defined data types (UDTs). This section describes the default SQLData interface and how to override the default.
  - 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.

Java™ virtual processors

Java™ UDRs execute on specialized virtual processors called Java™ virtual processors (JVPs). A Java™ Virtual Machine (JVM) is embedded in the code of each JVP.

The JVPs are responsible for executing all server-based Java™ UDRs and applications. Although the JVPs are used for Java-related computation, they have the same capabilities as a CPU VP, and they can process all types of SQL queries. This eliminates the need to ship Java-related queries back and forth between CPU VPs and JVPs.

Thread scheduling

When the JVP starts the JVM, the entire database server component is thought of as running on one particular Java™ thread, called the main thread. The JVM controls the scheduling of Java™ threads and the database server scheduler multiplexes HCL Informix® threads on top of the Java™ main thread. In other words, the Informix® thread package is stacked on top of the Java™ thread package.

Query parallelization

While Java™ applications use threads for parallelism, the Informix® database server uses threads for overlapping latency. That is, Informix® threads run concurrently but not in parallel. To parallelize a query, the database server must spread the work among multiple virtual processors.

Consequently, the database server must have multiple instances of JVPs to make parallel calls to UDRs written in Java™ code. Because the JVMs embedded in different VPs do not share states, you cannot store global states by using Java™ class variables. All global states must be stored in the database to be consistent. The only guarantee from the database server is that any given UDR instance executes from start to finish on the same VP. The database server enforces a round-robin scheduling policy where the UDR instances are spread over the JVPs before they start executing.

The consistency of multiple JVMs is not an issue on the Windows™ platform because all VPs are mapped to kernel threads instead of processes. Because all VPs share the same process space, you do not need to start multiple instances of the JVM.