> # Planning Client Data Sources

> Configuring SequeLink Client data sources is a simple task, but before you configure the data sources, you must make the following decisions:

> - You must decide which server connection method to use- direct connection or retrieving the connection parameters from a Lightweight Directory Access Protocol (LDAP) directory.
> - You must decide whether to reference the default server data source or another server data source.

> ### Planning ODBC Client and ADO Client Configurations

> On Windows platforms, ensuring that multiple ODBC or ADO Clients have the same configuration is an easy task when you create a predefined client installation image called a Quick Install image. After you define a Quick Install image, users can install this image on their client machines.

> #### Configuring Quick Install Images

> A Quick Install image can be stored on a file server and used for all ODBC or ADO Client installations within a workgroup. Installing a Quick Install image requires minimal user interaction and ensures that every client for which you are responsible has the same configuration. You can also define multiple Quick Install images, which allows you to customize each image for different workgroups within your organization.

> When configuring a Quick Install image, you define the following information:

> - Whether the installation is a workstation or network installation
> - The location of the installation directory
> - Which SequeLink components to install
> - Which mode the installation will run in (interactive or batch)
> - Whether client data sources are installed (see "Including Client Data Source Configurations in Quick Install Images")

> Refer to the SequeLink Installation Guide for instructions on how to define a Quick Install image.

> #### Including Client Data Source Configurations in Quick Install Images

> As part of a Quick Install image, you can specify client data sources that are to be installed on the client machines, which ensures that each client has the same client data source configuration. See "Planning Client Data Sources" for more information. The client data sources that are part of a Quick Install image first must be exported to a data source file using the SequeLink Data Source SyncTool Administrator. The SequeLink Data Source SyncTool Administrator allows you to create data source files and export data source definitions to data source files. Refer to the SequeLink Administrator's Guide for information about how to use the SyncTool and its administrator.

> To maintain client data source configurations, you can distribute a data source file and have users import the data source definitions from the data source file to their client machines. This ensures that the same client data source configuration is installed on all client machines.

> ### Planning for Connection Pooling

> To implement JDBC connection pooling for the JDBC Client, the JDBC application must use a DataSource object (an object implementing the DataSource interface) to obtain a connection instead of using the DriverManager class. A class implementing the DataSource interface may or may not provide connection pooling. A DataSource object registers with a JNDI naming service. Once a DataSource object is registered, the application retrieves it from the JNDI naming service in the standard way.

> The .NET data provider automatically implements connection pooling. No changes are needed.

> For information about creating a DataSource object and using the DataDirect Connection Pool Manager to create your own connection pooling implementation, refer to the SequeLink Developer's Reference.

> ### Planning Connection Failover

> You can customize the SequeLink Clients for connection failover by configuring a list of alternate servers that are tried if the primary server is not accepting connections. Connection attempts continue until a connection is successfully established or until all the alternate servers have been tried the specified number of times.

> Optionally, you can specify the following additional connection failover features:

> - The number of times the SequeLink Client attempts to connect to the primary and alternate SequeLink servers after the initial unsuccessful connection attempt. By default, the SequeLink Client does not retry. To set this feature, use the Connection Retry Count (ConnectionRetryCount) connection option.
> - The wait interval, in seconds, between attempts to connect to the primary and alternate database servers. To set this feature, use the Connection Retry Delay (ConnectionRetryDelay) connection option.
> - Whether the SequeLink Client will use client load balancing in its attempts to connect to primary and alternate SequeLink servers. If load balancing is enabled, the driver uses a random pattern instead of a sequential pattern in its attempts to connect. The default value is not to use load balancing. To set this feature, use the Load Balancing (LoadBalancing) connection option.

> For detailed information on configuring the connection failover features for each SequeLink Client, refer to the SequeLink Administrator's Guide.