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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.
Control the VP environmentThe routine manager executes your C UDR in a virtual-processor (VP) environment.
Lock a UDR
Lock a shared-object file in memoryIf the set of UDRs in a shared-object file requires a lot of initialization or uses external resources, it can be costly to have the routine manager continually load and unload this shared-object file. To prevent the routine manager from unloading a shared-object file, use the mi_module_lock() function.

Lock a shared-object file in memory

If the set of UDRs in a shared-object file requires a lot of initialization or uses external resources, it can be costly to have the routine manager continually load and unload this shared-object file. To prevent the routine manager from unloading a shared-object file, use the mi_module_lock() function.

When you call mi_module_lock() with an argument of MI_TRUE, you set the module-lock flag, which locks the shared-object file in memory. Therefore, the routine manager does not allow the shared-object file to be unloaded for any reason.

This feature enables a DataBlade® (or group of related UDRs) to prevent its shared-object file from being unloaded in any of the following cases:

On execution of the DROP FUNCTION, DROP PROCEDURE, DROP ROUTINE, or DROP DATABASE statements
In various transaction rollback scenarios

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