ODBC Server Reference Manual

Architecture Overview
HP NonStop ODBC Server Reference Manual—429151-002
2-31
SQL Communication Subsystem
SCS manages server classes, much as Pathway does. SCS starts and stops
servers according to configuration information. This task is done solely for
performance, to avoid excessive NEWPROCESS commands and SQL compilation
for client connections.
•
SCS provides a management interface.
SCS provides interfaces to the Subsystem Control Facility (SCF) and the Event
Management Service (EMS) to help administrators manage a NonStop ODBC
Server system.
Client Communication
After starting and initializing itself, a NonStop ODBC server opens SCS and uses
WRITEREAD to support both a logical Read and Write. A WRITEREAD is posted
when the NonStop ODBC server is ready to read a request message from the client.
After processing a request, WRITEREAD is used to send reply data to the client.
Figure 2-26 illustrates this communication process.
Figure 2-25. SCS Tasks
Client SCS
NonStop ODBC
Server
TCP/IP or
IPX/SPX or ...
Simple NonStop
ODBC IPC
EMS,
SCF
Interfaces
Many NonStop ODBC Servers
in Server Classes
VST029.vsd