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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
Manage memoryA C user-defined routine (UDR) has access to shared memory for dynamic allocations and stack memory for routine arguments (including the MI_FPARAM structure), local stack variables, and return values.
Manage stack spaceSession threads execute C UDRs and their thread-stack space is allocated from a common region in shared memory. The thread stack stores nonshared data for the UDRs and system routines that the thread executes. This stack contains everything that would normally be on the execution stack, including routine arguments (including the MI_FPARAM structure, local (stack) variables, and function return values.

Manage stack space

Session threads execute C UDRs and their thread-stack space is allocated from a common region in shared memory. The thread stack stores nonshared data for the UDRs and system routines that the thread executes. This stack contains everything that would normally be on the execution stack, including routine arguments (including the MI_FPARAM structure, local (stack) variables, and function return values.

Like all memory that UDRs use, stack segments can be overrun. The database server can only check for stack violations when the UDR yields. Therefore, you must ensure that you perform the following tasks within a UDR:

Efficiently manage stack space usage in your UDR
Limit usage of stack space in your UDR and ensure sufficient stack-space allocation when you register the UDR.
Use the mi_call() function for UDRs that potentially use unlimited recursion.

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