Connecting to a Database

To perform a request, the driver manager and driver must manage the information for the development environment, each application connection, and the SQL statement. The pointers that return this information to the application are called handles. The APIs must include these handles in each function call. Handles used by the development environment include these handles:

Handle	Purpose
HENV	The environment handle contains information related to the current database connection and valid connection handles. Every application connecting to the database must have an environment handle. This handle is required to connect to a data source.
HUSER	The user handle contains information related to a specific connection. Each user handle has an associated environment handle with it. A connection handle is required to connect to a data source. If you are using transaction processing, initializing HUSER indicates the beginning of a transaction.
HREQUEST	The request handle contains information related to a specific request to a data source. An application must have a request handle before executing SQL statements. Each request handle is associated with a user handle.