ODBC Server Reference Manual

Architecture Overview

HP NonStop ODBC Server Reference Manual—429151-002

2-18

Message Flows

To improve performance, the NonStop ODBC Server caches the reading of the

mapping tables so that message 4 can often be omitted. When SCS is dynamically

configured while in operation, the cache is reset to an empty state.

If the client SQL statement is a stored procedure execution, Step 4 involves mapping

the stored procedure name to a Pathway system and the server class that contains the

Figure 2-18. Message Flow for Client SQL Execution

1, 2 Client executes SQL statement at the API; a message is sent to SCS

containing the statement.

3 SCS forwards the message, without examining its contents, to the appropriate

NonStop ODBC server.

4 The NonStop ODBC server translates the SQL statement from Transact-SQL

or CORE SQL to NonStop SQL/MP. This involves mapping (translating) certain

names, such as table names, from TSQL or CORE form to NonStop SQL/MP

form. To do this, the NonStop ODBC server uses NonStop SQL/MP to access

the mapping tables.

5 The NonStop ODBC server executes the client’s statement. This often involves

executing NonStop SQL/MP statements against the database.

6 The NonStop ODBC server translates the result data (or error message) from

NonStop SQL/MP form to TSQL or CORE SQL form and sends a reply.

7, 8 The reply is sent to the client and the results or error message are returned

through the API.

NonStop ODBC

Mapping and

Configuration

Tables

Communication

Processes

SCS

Client

Executing

NonStop ODBC

Server

1 2 3

678

NonStop

SQL/MP

Objects

NonStop SQL/MP

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