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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.
Symbols in shared-object filesThe database server resolves undefined symbols in a shared-object file when it loads the shared-object file. If a symbol is missing, the load fails on the first execution of the UDR, and the database server writes a message in the log file. Symbols defined in two different shared-object files are distinct entities and do not resolve against each other.

Symbols in shared-object files

The database server resolves undefined symbols in a shared-object file when it loads the shared-object file. If a symbol is missing, the load fails on the first execution of the UDR, and the database server writes a message in the log file. Symbols defined in two different shared-object files are distinct entities and do not resolve against each other.

A symbol defined in both a shared-object file and the HCL Informix® main module behaves in one of two ways:

If the symbol referenced in the shared-object file is in the same source file that references it, the debugger accesses the symbol in the shared object file, as expected.
If the shared-object file includes more than one source file and a cross-file symbol reference exists, the symbol is resolved to the main module of the database server.

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