Well If you have really managed your n-tier architecture in the way it should be then you need not to worry a lot. You have to change -
1) Connection string and connection related settings in Web.Config
2) You have to include oracle data providers instead to SqlHelper or SqlClient.
3) You need to change your database interacting classes for oracle interaction.
BLL and UI will remain the same.
Better you use -
1) Oracle data provider for .net
2) Ms Enterprise library 3.1
Hope it helps.
Hope it helps.
-Manas
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