PRODUCT SUMMARY

Introduction

Heterogeneous data access is a problem that affects a lot of companies. Many of them run several different database systems. Each of these systems stores data and has a set of applications that run against it. Consolidation of this data in one database system is often hard - in large part due to the fact that many of the applications that run against one database may not have an equivalent that runs against another. Until such time as migration to one consolidated database system is made feasible, it is necessary for the various heterogeneous database systems to interoperate. The challenge is to quickly, efficiently, and economically deploy data that may exist on many disparate systems through a single application, providing a comprehensive view of the data, regardless of the database or operating system. Oracle offers two connectivity solutions for the heterogeneous environment. They are: Oracle Generic Connectivity and Oracle Transparent Gateways.

Both Generic Connectivity and Transparent Gateways provide the ability to transparently access data in non-Oracle systems from an Oracle environment. This transparency eliminates the need for application developers to customize their applications to access data from different non-Oracle systems, thus decreasing development efforts and increasing the mobility of the application. Applications can be developed using a consistent Oracle interface for both Oracle and non-Oracle systems.

For smooth interoperability between disparate systems, SQL translations, data dictionary translations and data type translations are required, even if the non-Oracle systems are based on SQL standards. Both Generic Connectivity and Transparent Gateways have the ability to translate one system's dialect to another.

Gateway technology is composed of two parts: a component that has the generic technology to connect to a non-Oracle system, which is common to all the non-Oracle systems, called Heterogeneous Services (HS) and a component that is target specific, called an Agent. Heterogeneous Services in conjunction with the Agent enables transparent access to non-Oracle systems from an Oracle environment.

Heterogeneous Services Technology

Heterogeneous Services provides the generic technology for connecting to non-Oracle systems and is the processing power of both solutions. Generic Connectivity and Transparent Gateways are based on Heterogeneous Services. As an integrated component of the database, Heterogeneous Services can exploit features of the database, such as the powerful SQL parsing and distributed optimization capabilities.

Heterogeneous Services extend the Oracle SQL engine to recognize the SQL and procedural capabilities of the remote non-Oracle system and the mappings required to obtain necessary data dictionary information. It provides two types of translations: the ability to translate Oracle SQL into the proper dialect of the non-Oracle system as well as data dictionary translations that displays the metadata of the non-Oracle system in the local format. For situations where no translations are available, native SQL can be issued to the non-Oracle system using the pass-through feature of Heterogeneous Services.

Heterogeneous Services also maintains the transaction coordination between Oracle and the remote non-Oracle system, such as providing the two-phase commit protocol to ensure distributed transaction integrity, even for non-Oracle systems that do not natively support two-phase commit.

Agent

The capabilities, SQL mappings, datatype conversions, and interface to the remote non-Oracle system are contained in the Agent. The agent interacts with Heterogeneous Services to provide the transparent connectivity between Oracle and non-Oracle systems. There are two types of agents: HS agents and Transparent Gateway agents.

There are two types of HS agents: HS ODBC that uses an OBDC driver to talk with the non-Oracle system and HS OLEDB that uses an OLEDB driver. HS agents are part of the Oracle database, so they are installed by default with the database. Generic Connectivity uses these agents to connect to the non-Oracle systems.

Transparent Gateway agents are separate from the Oracle server. Unlike the HS agents, which are on the same machine as the Oracle database, the Transparent Gateway agents can be installed on any machine. They can be on the same machine as the Oracle database or on the same machine as the non-Oracle system or on a third machine as a stand-alone. Each configuration has its advantages and disadvantages. The issues to consider when determining where to install these agents are network traffic, operating system platform availability, hardware resources and storage. For maximum performance and functionality, Transparent Gateways use the native interfaces to communicate with non-Oracle systems.

Oracle Generic Connectivity

Generic Connectivity is a feature of the Oracle database. It is a generic solution that uses an ODBC or OLE DB driver to access any ODBC or OLEDB compliant non-Oracle system. It addresses the needs of data access to many data stores for which Oracle does not have a gateway solution. This feature enables transparent connectivity using industry standards such as ODBC and OLEDB. Oracle Generic connectivity makes it possible to access low-end data stores such as Foxpro, Access, dBase and non-relational targets like Excel.

Oracle Transparent Gateways

In contrast to Generic Connectivity, which is a generic solution, Transparent Gateways are tailored solutions, specifically coded for the non-Oracle system. They provide an optimized solution, with more functionality and better performance than Generic Connectivity. Generic Connectivity relies on industry standards, whereas Transparent Gateways accesses the non-Oracle systems using their native interface. Transparent Gateways are also end-to-end certified. Oracle has transparent gateways to many sources, DB2, Sybase, Informix, Microsoft SQL Server, Ingres, Teradata to name a few.

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