connected data needs connection to be created to access hence slower while disconnected is in memory data thats faster access.to access connected data you use ADO.NET whereas for disconnected you do not use.disconnected-data can be accessed from multiple tables in a dataset. connected- .net runtime creats an instance of the datatable to hold data.

Disconnected data-

It means it release the process data from database to application at once it fill to the memory then no connection with the database (connection close).

E.g. when we retrieve data set from database it directly fills it to the memory and then application gets the data from the memory.

Connected data-

It gives the process data to the application continuously without getting the data from memory. e.g. when we retrieve data to data reader, once received the data row from the database then it give the next one also from the database likewise it gives continues data to the application from database.-By pubudu hatangala