Oracle Data Access Components Overview

Oracle Data Access Components (ODAC) is a library of components that provides native connectivity to Oracle from Delphi, Delphi for .NET, C++Builder, Kylix, and Free Pascal. The ODAC library is designed to help programmers develop faster and cleaner Oracle database applications.

ODAC is a complete replacement for standard Oracle connectivity solutions and presents an efficient native alternative to the Borland Database Engine and dbExpress for access to Oracle.

Advantages of ODAC Technology

ODAC is a direct connectivity database wrapper built specifically for the Oracle server. ODAC offers wide coverage of the Oracle feature set, supports both Client and Direct connection modes, and emphasizes optimized data access strategies.

Wide Coverage of Oracle Features

By providing access to the most advanced database functionality, ODAC allows developers to harness the full capabilities of the Oracle server and optimize their database applications. ODAC stands out as the set of components with the widest support of Oracle functionality. It is the only component library to support Oracle distributed transactions and implements support for controlling statement caching, OCI pooling, and Oracle Advanced Queuing.

Native Connection Options

ODAC offers two connection modes to the Oracle server: connection through the Oracle Call Interface in Client mode and direct connection over TCP/IP in Direct mode. ODAC-based database applications are easy to deploy, do not require installation of other data provider layers (such as BDE), and tend to be faster than those that use standard data connectivity solutions.

Optimized Code

The goal of ODAC is to enable developers to write efficient and flexible database applications. The ODAC library is implemented using advanced data access algorithms and optimization techniques. Classes and components undergo comprehensive performance tests and are designed to help you write high-performance, lightweight data access layers. To see results of ODAC performance tests, visit the ODAC performance page.

Compatibility with Standard Data Access Components

The ODAC interface retains compatibility with standard VCL data access components like BDE. Existing BDE-based applications can be easily migrated to ODAC and enhanced to take advantage of Oracle-specific features like alerts, pipes, and the direct-path interface. Project migration can be automated with the BDE Migration Wizard.

How Does ODAC Work?

ODAC allows you to connect to Oracle in two ways: in Client mode, using Oracle client software, or in Direct mode, over TCP/IP.

In Client mode, ODAC connects to Oracle through the Oracle Call Interface (OCI). OCI is an application programming interface that allows an application developer to use a third-generation language's native procedure or function calls to access the Oracle database server and control all phases of SQL statement execution. OCI is a library of standard database access and retrieval functions in the form of a dynamic-link library.

In Direct mode, ODAC connects to Oracle directly without using Oracle client software. In this mode, ODAC requires only TCP/IP support, and lets you build really thin database applications.

In comparison, the Borland Database Engine (BDE) uses several layers to access Oracle, and requires additional data access software to be installed on client machines.

The BDE data transfer protocol is shown below.

BDE Connection Protocol

Using ODAC in Client mode allows your application to connect to OCI directly.

ODAC Connection Flow [Client Mode]

Using ODAC in Direct mode provides the optimal transfer route.

ODAC Connection Flow [Direct Mode]

Key Features

The following list describes the main features of Oracle Data Access Components.

• Direct access to server data. Does not require installation of other data provider layers (such as BDE and ODBC)
• In Direct mode does not require Oracle client software and works directly through TCP/IP
• VCL, VCL.NET, and CLX versions of library available
• Full support of the latest versions of Oracle
• Support for all Oracle data types
• Disconnected Model with automatic connection control for working with data offline
• Local Failover for detecting connection loss and implicitly re-executing certain operations
• Oracle Transparent Application Failover support
• All types of local sorting and filtering, including by calculated and lookup fields
• Automatic data updating with TOraQuery, TSmartQuery, and TOraTable components
• Unicode and national charsets support
• Distributed transaction support
• Oracle Advanced Queuing support
• Support for many Oracle-specific features, such as alerts, pipes and direct path interface
• Advanced script execution functionality with TOraScript component
• Support for using Macros in SQL
• Integration with OraDeveloper Tools for performing advanced database development and administration tasks
• Easy migration from BDE with Migration Wizard
• Lets you use Professional Edition of Delphi, C++Builder, and Kylix to develop client/server applications
• Includes annual ODAC Subscription with Priority Support
• Licensed royalty-free per developer, per team, or per site

See All Features

Connecting in Direct Mode

By default, ODAC, like most applications that work with Oracle, uses the Oracle Call Interface (OCI) to connect to the Oracle database server. This is referred to as connecting in Client mode, and it is the usual way to develop Oracle applications with a third-generation language. All OCI routines are stored in external libraries, so the executables for applications that work through OCI are small. However, working through OCI requires Oracle client software to be installed on target workstations. This is an inconvenience and causes additional installation and administration expenses. Furthermore, there are some situations in which installation of Oracle client is not advisable or may even be impossible; for example, when deploying an application to remote machines which do not have qualified administration.

To overcome these problems, ODAC Developer Edition and ODAC Professional Edition include an option to connect to Oracle directly over the network using the TCP/IP protocol. This is referred to as connecting in Direct mode. Connecting in Direct mode does not require Oracle client software to be installed on target machines. The only requirement for running an ODAC-based application that uses the Direct mode is that the operating system must have TCP/IP support.

ODAC Design-Time View