ODBC Server Reference Manual

Architecture Overview
HP NonStop ODBC Server Reference Manual—429151-002
2-8
Databases and Datasources
a vendor-neutral term, avoiding the need to distinguish among connecting to a
database, connecting to a server that accesses a database, and connecting to
anything else.
When an ODBC client connects to a datasource, the ODBC driver manager on the PC
accesses a special ODBC.INI file, or the ODBC registry for Windows NT or Windows
95, to get information about the datasource. The file indicates which ODBC driver to
load to access the datasource. The file can contain other information, such as the
actual server to connect to (in the case of SQL Server), the database name to use, and
so on.
In Figure 2-9, if the client connected to the datasource named CUSTOMERS, the
Nonstop ODBC/MP driver \ODBC\TDMSRVR.DLL would be loaded. The driver would
then read the ODBC.INI file and determine that database CUST1 should be used with
a user ID of SMITH. Microsoft documents this use of the ODBC.INI file, but other
schemes are possible (the driver could communicate with a name server to bind the
datasource name, and so on).
Figure 2-8. Database View for an ODBC Client
Figure 2-9. Interpreting an ODBC Datasource
PEOPLE
JOBS
Datasource CUSTOMERS
CUSTOMERS
ORDERS
SQL Catalog
Client
Application
VST012.vsd
Datasource CUSTOMERS
CUSTOMERS
ORDERS
SQL Catalog
Datasource CUSTOMERS
Driver = c:\odbc\tdmsrvr.dll
Database = cust1
TCP/IP addr = 34...
UserID = Smith
ODBC.INI File
Client
Application
VST013.vsd