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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®.
Database access
Connection handlingThis section describes how to initialize, establish, and close connections.
Initializing a client connectionBefore a client LIBMI application can establish a connection, it must initialize the connection with the name of the database server and database to which it needs to connect.
Connection parametersTo indicate which database server the client LIBMI application needs to connect to, the application uses connection parameters. The DataBlade® API provides a connection-information descriptor, MI_CONNECTION_INFO, to access connection parameters.
Establish default connection parametersThe default connection parameters identify to which database server to connect. Before you establish a connection, determine whether you want to use the system-default connection parameters or default connection parameters that you specify.
System-default connection parametersThe database server obtains values for the system-default connection parameters from the execution environment of the client LIBMI application. When you use system-default connection parameters, you enable your application to be portable across client/server environments. However, before the application begins execution, you must ensure that the client/server environment is correctly initialized.

System-default connection parameters

The database server obtains values for the system-default connection parameters from the execution environment of the client LIBMI application. When you use system-default connection parameters, you enable your application to be portable across client/server environments. However, before the application begins execution, you must ensure that the client/server environment is correctly initialized.

The following table shows the system-default connection parameters that the database server uses to establish a connection.

Table 1. System-default connection parameters
System-default connection parameter	System-default connection value
Database server name	INFORMIXSERVER environment variable
Server locale (Server)	SERVER_LOCALE environment variable or default locale (en_us)
(Client) Database locale	DB_LOCALE environment variable or default locale (en_us)

The system-default connection parameters provide connection information for all connections made within a client LIBMI application unless you explicitly override them within the application.

To use the default database server, initialize the server_name field to a NULL-valued pointer and server_port to zero.

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