The following figure illustrates how the interface libraries assemble the list of connection parameters they will use to establish a connection.
Key points from the figure are as follows:
Precedence — Parameters held in more than one place are subject to the following order of precedence:
Connection string
SQLCONNECT
Data source
That is, if a parameter is supplied both in a data source and in a connection string, the connection string value overrides the data source value.
Failure — Failure at this stage occurs only if you specify in the connection string or in SQLCONNECT a data source that does not exist in the client connection file.
Common parameters — Depending on other connections already in use, some connection parameters may be ignored, including:
The interface library uses the completed list of connection parameters to attempt to connect.
