Data Source is an ODBC Connection

Some ODBC drivers do not support bulk fetch.
If the table has blob fields use SQL as source and put blob fields last
“Select field1,blob1,blob2 from table” 

It also possible to use ODBC connection strings for both Reader and Writer connections. For example for MS SQL Server connection string is:

Driver={SQL Native Client};Server=myServerAddress;Database=myDataBase;Uid=myUsername;Pwd=myPassword;

One of the major benefits of using connection strings that it makes it no longer necessary to create ODBC Dsn’s manually on every single computer where Visual Importer ETL is installed. It also gives a greater control over the connection parameters.

Note: Leave username and password blank and provide it within the connection string

More information about connection strings can be found at: http://www.connectionstrings.com

The simplest way to create ODBC connection string is to use ODBC Connection builder dialogue. Double click on ODBC driver name to create a connection string