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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.
Database parametersTo indicate which database it needs to connect to, the client LIBMI application uses database parameters. The DataBlade® API provides a database-information descriptor, MI_DATABASE_INFO, to access database parameters. This data type structure identifies the database for a particular session.
Establish default database parametersThe default database parameters identify the database and user for the connection. Before you establish a connection, you can determine whether you want to use the system-default database parameters or default database parameters that you specify.
Overriding the system-default database parameters

Overriding the system-default database parameters

About this task

The database server obtains values for the database parameters from the database-information descriptor. The database server initializes the database-information descriptor with the system-default database parameters in System-default database parameters. You can initialize your own database-information descriptor to override the default database parameters. When you override system-default database parameters, you enable your application to have database information that is independent of the client/server environment in which it runs.

To override the system-default database parameters:

Procedure

Allocate a database-information descriptor.
Fill the fields of the database-information descriptor with the default database parameters you need.
If you do not set a particular field, the database server uses the system-default value in System-default database parameters for the associated database parameter.
Pass a pointer to this database-information descriptor to the mi_set_default_database_info() function.

Results

The user-defined database parameters provide database information for all connections made within a client LIBMI application after these functions execute (unless the functions are called again to set new default values).

You can obtain existing default database parameters with the mi_get_default_database_info() function. This function populates a user-defined database-information descriptor with the current default database parameters.

Server only: In a C UDR, mi_get_default_database_info() obtains the same information as mi_get_database_info(). The mi_set_default_database_info() function is ignored.

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