ODBC, and further developments such as JDBC, OLEDB, define a low-level set of calls which allow client applications and servers applications to exchange instructions and share data without needing to know anything about each other. It applies to any Client-Server operation, whether or not the client and server applications are resident on the same machine, or on different PC's, or even if the server is on a remote machine running a different operating system.
This chapter introduces OpenLink's offerings to provide these technologies to you.
OpenLink Universal Data Access (UDA) Multi Tier consists of three main components, of varying types:
One client driver connecting to a variety of data sources.
Responsible for managing connections between Generic Clients and Server Agents. The Request Broker is completely configurable and its responses to incoming requests from Clients controlled by the Sessions Rules Book (oplrqb.ini).
Task specific applications exclusively launched by the Request Broker for Generic Clients to communicate with, and facilitate their needs.
one specific for each database and major version as required: Oracle, Progress, Ingres, Postgres, SQL Server, etc...
special agent for forwarding requests to another Request Broker, particularly useful on firewalls.
Special case of Database Agent where another ODBC datasource is the database.
The Request Broker and Server Agents are typical addressed as the server components. This is a logical distinction because the client and server can be the same machine. In testing environments this is often the case.
The Request Broker is responsible for brokering the services of OpenLink Data Access and Service Providing Agents. It is also the component responsible for coordinating and controlling your entire OpenLink Data Access session irrespective of Data Access mechanism being used. This is the heart and soul of the OpenLink Database Independent Communications Layer. It is the technology that enables the OpenLink Data Access drivers to communicate with your backend database engines alleviating the need to acquire additional database specific networking software from your backend database vendor(s). More than one Broker may exist on a system if each instance is defined separately.
One or more Database Agents (one for each supported database engine) are database specific components that provide the actual backend database connectivity and data access services to your OpenLink Data Access Clients (ODBC, JDBC, UDBC, OLE-DB etc.). These components are actually clients from the perspective of each supported backend database, this is because they are built using the Call Level Interfaces (CLIs) or Embedded SQL interfaces of these backend databases.
Service Provider Agents (ODBC, JDBC, PROXY) are generic agents that provide Distributed Data Access Protocol handling services to OpenLink Data Access Drivers. The data access protocols supported are as follows:
ODBC Agent - enabling OpenLink Multi-Tier ODBC Drivers to connect to local or remote non OpenLink ODBC Drivers
JDBC Agent - enabling OpenLink JDBC Drivers to connect local or remote OpenLink or non OpenLink ODBC or UDBC Drivers
PROXY Agent - enabling all OpenLink Data Access Clients to connect to OpenLink Database Agents that do not reside on the same server machine as the prime OpenLink Request Broker. The prime Broker being the Request Broker that all your OpenLink Clients are configured to request data access services from. This enables you to configure your OpenLink Database Agents for use in N-Tier distributed computing environments.
An architectural overview of the OpenLink Multi-tier Data Access infrastructure is available at: www.openlinksw.com/info/mtproduct.htm. Note that the OpenLink Request Broker is the core component that makes up the OpenLink Database Independent Communications Layer in this illustration.
The components listed above are presented to you for download at the end of your interaction with the OpenLink Software Download Wizard.
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