ODBC Server Reference Manual

Architecture Overview
HP NonStop ODBC Server Reference Manual—429151-002
2-7
Databases and Datasources
The advantages of supporting both clients with one architecture are simplicity of design
and the opportunity to provide shared objects for the various clients. Note that clients
of just one type are unaffected by NonStop ODBC Server extensions. For example, if a
system has only TSQL clients, they do not recognize names over 32 characters long.
Databases and Datasources
The following description of databases and datasources is based on the client-side
view, but it also covers enough of the server-side view to indicate the NonStop ODBC
Server implementation.
Both DBLIB and ODBC clients make a connection to where their data is maintained. In
ODBC the connection is to a datasource, for DBLIB it is a server. Both are local logical
identifiers that translate into a unique network server name and server location. The
database view (what a database is, how it is named) is slightly different for each client
type; descriptions of both follow.
Both types of clients treat a database as an object that has a name, has a catalog of
SQL objects, maintains the SQL objects, can process SQL statements, and can handle
transactions.
The DBLIB client actually connects to a particular SQL Server that manages a set of
databases, as shown in Figure 2-7. The connection requests can specify the particular
database to connect to (there are also commands to switch to another database). The
set of databases always contains a special master database that catalogs the other
databases as well as other information pertinent to the SQL Server. The master
database corresponds to the NonStop SQL/MP system catalog.
The ODBC client recognizes a set of datasources and can connect to one of them, as
shown in Figure 2-8. A datasource is essentially a database. All the datasources are
independent (there is no master database, as with DBLIB). Datasource is meant to be
Figure 2-7. Database View for a DBLIB Client
PEOPLE
JOBS
CUSTOMERS
ORDERS
SYSOBJECTS
Database CUSTOMERS
SQL Server
Client
Application
CUSTOMERS
Database MASTER
SYSDATABASES
SYSOBJECTS
VST011.vsd