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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.
Shared memoryWhen a C UDR executes in a virtual processor (VP), it allocates memory from the shared memory of the database server.
Choose the memory duration
Public memory durationsThe DataBlade® API memory-management functions support several public memory durations. A UDR can use a public memory duration for most dynamic allocations of memory.

Public memory durations

The DataBlade® API memory-management functions support several public memory durations. A UDR can use a public memory duration for most dynamic allocations of memory.

The DataBlade API provides the public memory durations that the following table shows.

Table 1. Public memory durations
Public memory duration	Memory-duration constant	Description
For the duration of one iteration of the UDR	PER_ROUTINE, PER_FUNCTION	The database server frees the memory after the UDR returns.
For the duration of the current SQL subquery	PER_COMMAND	The database server frees memory when an SQL command terminates.
For the duration of the current SQL statement	PER_STATEMENT (Deprecated)	The database server frees memory when an SQL statement terminates.
For the duration of the execution of the current SQL statement	PER_STMT_EXEC	The database server frees memory when the execution of an SQL statement is complete.
For the duration of the current prepared SQL statement	PER_STMT_PREP	The database server frees memory when a prepared SQL statement terminates.

The PER_ROUTINE and PER_COMMAND memory durations are the most common for C UDRs. The memory-duration constants in Public memory durations are of type MI_MEMORY_DURATION, which the memdur.h header file defines. All memory-duration constants in Public memory durations are also declared in the memdur.h header file.

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