如何避免在LINQ 2 SQL中升级为MSDTC

Question

I have following situation :

• application uses 2 databases

• at some point, I need to use a transactionscope:

  insert record table A database X

  insert record table C database Y

  submitchanges

  insert record table B database X (one of the fields of B has the value of the primary key id of A that's why I need to call submitchanges)

  submitchanges

  A & B must both be successfull, or fail together. C doesn't matter. Insert on C does trigger the error MSDTC is nog available. But I don't want C to be part of the transaction ( for whatever reason ) I know that normally when they would be a relationship between A and B, the value (FKid) would be filled automatically, but I can not use FK relationship in this case. (I guess there is no way of getting the id of a into b without using FK?)

  I tried to specify enlist=false on the connectionstring of Y only, or even on both X and Y but I still get the error.

Answer 1

MSDTC is the distributed transaction coordinator. When you attempt to update multiple databases within a transaction, the transaction will be escalated to MSDTC. MSDTC must be enabled on the database server(s) and the client, I believe. If you want to avoid this escalation, you'll need to have two separate transactions (using two separate connections), one for database X and one for database Y.

Answer 2

When a transaction is promoted from a local transaction to a distributed transaction is in my opinion not always easy to know, and I have experienced places where I would expect it to be a local transaction, where it has been promoted to a distributed transaction, requiring DTC.

However, explicitly running the insert into database Y in a different transaction could solve the issue. You can then explicitly specify a transaction with TransactionScope.Suppress or TransactionScope.RequiresNew :

http://msdn.microsoft.com/en-us/library/system.transactions.transactionscopeoption.aspx

// Update table A in database X
// ...


using(TransactionScope scope = new TransactionScope(
          TransactionScopeOption.RequiresNew
    ))
{
   // Update table C in database Y
   ...
   scope.Complete();
}

// Update table B in database X

However, ask yourself, is the insert into table C on database Y totally independent on the first insert in table A in database X? If not, what if the insert into table B in database X fails, is the insert into table C on database Y still valid? Or might you end up with inconsistent data? And, if so, does it matter enough for you to bring DTC into the soup?