ODBC Server Reference Manual

Architecture Overview
HP NonStop ODBC Server Reference Manual—429151-002
2-33
SQL Communication Subsystem
number of free servers. There is also a special DEFAULT server class to handle clients
that are not configured for a specific server class.
Figure 2-27 shows two server classes, each with two NonStop ODBC servers. Two
clients are connected, one to each server class.
The ZNSSER table contains the server class configuration information used by SCS to
start each NonStop ODBC server process. At start-up time, SCS gets the configuration
information from NOSUTIL and sends each new NonStop ODBC server process a
message containing this information. The NonStop ODBC server completes its
initialization and replies to SCS that it is up. SCS then places the new NonStop ODBC
server process in the pool of available servers.
When SCS first starts a NonStop ODBC server process, the new server process runs
under the same user ID as the SCS process.When a client connects to a NonStop
ODBC server, the server process calls the Guardian USER_AUTHENTICATE_
procedure to validate the client’s username and password. If the validation is
successful, the NonStop ODBC server switches to the user ID of the connected client.
The client can then send requests to the NonStop ODBC server.
Figure 2-28 shows the initialization of an NonStop ODBC server process.
Figure 2-27. SCS Management of Server Classes
NonStop
ODBC
Server
processor = 1
Server Class CLASS1
Guardian Name = G1.U1
CPU = (0,1)
Server Class DEFAULT
CPU = (1,2)
SCS Configuration
Client 1
Client 2
SCS
NonStop
ODBC
Server
processor = 0
NonStop
ODBC
Server
processor = 1
NonStop
ODBC
Server
processor = 2
SC = CLASS1
(Client 1)
SC = CLASS1
(Idle)
SC = DEFAULT
(Client 2)
SC = DEFAULT
(Idle)
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