EF and TransactionScope for both SQL Server and Oracle without escalating/spanning to DTC?

Question

Can anyone update me on this topic?

I want to support both SQL Server and Oracle in my application.

Is it possible to have the following code (in BL) working for both SQL Server and Oracle without escalating/spanning to distributed transactions (DTC) ?

 // dbcontext is created before, same dbcontext will be used by both repositories
 using (var ts = new TransactionScope())
 {
    // create order - make use of dbcontext, possibly to call SaveChanges here
    orderRepository.CreateOrder(order);

    // update inventory - make use of same dbcontext, possibly to call SaveChanges here
    inventoryRepository.UpdateInventory(inventory);

    ts.Complete();
 }

As of today, end of August 2013, I understand that it works for SQL Server 2008+ ... but what about Oracle? I found this thread... it looks like for Oracle is promoting to distributed transactions but is still not clear to me.

Does anyone have experience with writing apps to support both SQL Server and Oracle with Entity Framework to enlighten me?

Thanks!

Update: Finally I noticed EF6 comes with Improved Transaction Support. This, in addition to Remus' recommendations could be the solution for me.

Answer 1

First: never use var ts = new TransactionScope(). Is the one liner that kills your app. Always use the explicit constructor that let you specify the isolation level. See using new TransactionScope() Considered Harmful.

Now about your question: the logic not to promote two connections in the same scope into DTC relies heavily on the driver/providers cooperating to inform the System.Transactions that the two distinct connections are capable of managing the distributed transaction just fine on their own because the resource managers involved is the same. SqlClient post SQL Server 2008 is a driver that is capable of doing this logic. The Oracle driver you use is not (and I'm not aware of any version that is, btw).

Ultimately is really really really basic: if you do not want a DTC, do not create one! Make sure you use exactly one connection in the scope. It is clearly arguable that you do not need two connections. In other words, get rid of the two separate repositories in your data model. Use only one repository for Orders, Inventory and what else what not. You are shooting yourself in the foot with them and you're asking for pixie dust solutions.

Update: Oracle driver 12c r1:

"Transaction and connection association: ODP.NET connections, by default, detach from transactions only when connection objects are closed or transaction objects are disposed"

Answer 2

Nope, DTC is needed for distributed transactions - and something spanning 2 different database technologies like this is a distributed transaction. Sorry!