> # 1 Introduction

> DataDirect SequeLink is a middleware product that provides point-to-point connections from client to server for the latest data access standards-Open Database Connectivity (ODBC 3.52), JDBC 3.0, ActiveX Data Objects (ADO 2.7), and Microsoft .NET 1.1. In addition, SequeLink allows you to centrally configure your data access environment and manage data access activity.

> Today's complex Information Technology (IT) environments require data access components that provide superior interoperability, performance, and manageability. SequeLink middleware fulfills these requirements by providing the following key advantages for complex IT environments:

> - Data Connectivity. SequeLink provides universal data connectivity for the latest ODBC, JDBC, ADO, and .NET standards to a variety of data stores, including mainframe data. Additionally, SequeLink supports distributed transactions for Microsoft Distributed Transaction Coordinator (MS DTC) and Java Transaction API (JTA). SequeLink's component implementation allows you to manage your entire data access environment regardless of the operating systems on which the SequeLink components run. In addition, SequeLink Client is database-independent-no extra client components are required if you decide to incorporate additional data store technologies in your data access infrastructure.
> - Interoperability. SequeLink allows you to leverage existing and evolving technologies by adhering to industry standards rather than a proprietary standard. In addition to supporting the latest data access standards, SequeLink allows you to use Lightweight Directory Access Protocol (LDAP) for centralized connection and configuration information.
> - Security. The messages between SequeLink middleware components that involve data requests and data transmitted over a network, Internet, or Intranet can be scrambled or, in some cases, encrypted. In addition, SequeLink supports authentication mechanisms provided by the database or by the operating system on which the SequeLink components run, such as Integrated NT Security on Windows and Resource Access Control Facility (RACF) on z/OS. SequeLink also supports a variety of other security mechanisms such as Kerberos authentication to create a single-sign on environment, Secure Sockets Layer (SSL) data encryption, and read-only data store connections to keep the data in your data store secure from updates.
> - Systems management. SequeLink delivers key Reliability, Availability, and Serviceability (RAS) by providing dynamic service attributes. The majority of SequeLink's service configuration attributes are dynamic, meaning that if you change a setting for an attribute, the change takes affect immediately. SequeLink Clients provide connection failover and client load balancing features to further enhance availability and reliability.
> - Scalability. SequeLink provides superior performance and scalability through connection pooling at the client, through efficient use of server resources, and through its configurable multi-threaded implementation, which uses a dynamic worker thread model.

> This chapter introduces some concepts that will help you use SequeLink to provide data access across your enterprise.