> # SequeLink® Environment

> Today's data access computing environments typically involve multiple and disparate data stores accessed over a variety of infrastructures. In addition, many businesses are relying more on the Internet to provide access to corporate data for their employees, customers, and partners.

> SequeLink simplifies data access middleware requirements by providing data access for multiple data stores with a single client component as shown in Figure 1-2.

> Figure 1-2. SequeLink Middleware Solution for Data Access

> ### Providing Data Access

> ODBC, ADO, JDBC, and .NET are application programming interfaces (APIs) that allow developers to develop, compile, and ship an application without targeting a specific type of data store. Developers can use SequeLink as the middleware that allows their applications to access data from a choice of supported data stores. SequeLink provides ODBC, ADO, JDBC, and .NET data access from a client workstation directly to a server running the SequeLink Server software or from a Web/application server to a server running SequeLink Server as shown in Figure 1-3.

> Figure 1-3. SequeLink Data Access in Client/Server and Web/Application Server Environments

> ### Using SequeLink® to Link an Application to a Data Store

> Typically, a data access application accesses a SequeLink Server (specifically, a SequeLink data access service) by specifying a client data source that provides connection information to a specific server running SequeLink Server. SequeLink uses two different types of data sources-server data sources and client data sources.

> #### Server Data Sources

> Server data sources are data sources configured on the SequeLink Server. These data sources contain settings that affect how the SequeLink service operates and settings that affect how data is accessed by SequeLink Clients. Centralizing this information on the server, instead of distributing it among hundreds of SequeLink Clients, provides easier management of your entire data access infrastructure. When you install SequeLink Server, a default server data source, named Default, is automatically created on the server. If necessary, you can modify the definition of the default server data source.

> #### Client Data Sources

> Client data sources are minimal data sources configured on the SequeLink Client that contain connection instructions to a SequeLink data access service. Client data sources are required when configuring the SequeLink Client for ODBC or the SequeLink Client for ADO. For SequeLink Client for JDBC, you can configure a client data source or a connection URL. For SequeLink Client for .NET clients, you configure a connection string.

> A client data source can be configured to retrieve connection information from an LDAP directory server (or from any JNDI-enabled directory service for JDBC applications). The connection information stored in an LDAP directory contains the IP address of the server that runs SequeLink Server. Therefore, if a database must be moved to a different server, the administrator does not have to reconfigure user applications or the client data sources that must now access the new server because the connection information is stored centrally in an LDAP directory. The administrator only needs to update the LDAP directory entries to allow the SequeLink Clients to connect to the new server.