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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
Develop a user-defined routineA C user-defined routine (UDR) is a UDR that is written in the C language and uses the server-side implementation of the DataBlade® API to communicate with the database server. C UDRs (functions and procedures) are implemented as C-language functions. DataBlade® modules often include C UDRs that are made available for use by registering them in the database.
Debug a UDRBecause a UDR runs as part of the database server process, the routine must not do anything that might negatively affect the running of the database server, such as exiting. This section provides information about how to use a C debugger to attach to a virtual processor, handle the debugging session of a C UDR, and use DataBlade® API tracing.
Running a debugging sessionYou can set breakpoints, examine the stack, resume execution, or carry out any other normal debugger commands.
Debugging hints

Debugging hints

When you need to debug a UDR, keep in mind the following considerations:

During the development of a UDR, to avoid interfering with the operation of the database server, develop UDRs on the client computer even if they are eventually intended to run from the database server process.
Examine the database server log file for messages that the database server generates when it executes the UDR.
The database server writes status messages to the message log file. By default, this file is named online.log. You can change the name of this file with the MSGPATH configuration parameter.
Use the UDR tracing facility to insert trace messages within the body of the function.
The database server puts these trace messages in a trace file when the UDR executes. For more information, see Tracing.
Simplify the UDR to create a good test case.
Good test cases are as simple as possible.
Install and register any required DataBlade® modules
If your execution environment includes DataBlade modules, you might want to first attempt debugging without these DataBlade modules so that the environment is as simple as possible. However, if this is not possible, make sure that you install and register any DataBlade modules that affect the execution of the UDR you are debugging. To install and register other DataBlade modules, such as the DataBlade modules included with HCL Informix®, see the instructions that accompany them.

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