SQLTransaction has completed error

Question

I got following error once in my application.

This SQLTransaction has completed; it is no longer usable

Stack Trace is attached below – It says about Zombie Check and Rollback.

What is the mistake in the code?

Note: This error came only once.

UPDATE

From MSDN - SqlTransaction.Rollback Method

A Rollback generates an InvalidOperationException if the connection is terminated or if the transaction has already been rolled back on the server.

From Zombie check on Transaction - Error

One of the most frequent reasons I have seen this error showing up in various applications is, sharing SqlConnection across our application.

CODE

public int SaveUserLogOnInfo(int empID)
{
        int? sessionID = null;
        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            connection.Open();
            SqlTransaction transaction = null;
            try
            {
                transaction = connection.BeginTransaction();
                sessionID = GetSessionIDForAssociate(connection, empID, transaction);

                    //Other Code

                //Commit
                transaction.Commit();
            }
            catch
            {
                //Rollback
                if (transaction != null)
                {
                    transaction.Rollback();
                    transaction.Dispose();
                    transaction = null;
                }

                //Throw exception
                throw;
            }
            finally
            {
                if (transaction != null)
                {
                    transaction.Dispose();
                }
            }
        }

        return Convert.ToInt32(sessionID,CultureInfo.InvariantCulture);

   }

Stack Trace

---

REFERENCE:

1. What is zombie transaction?
2. Zombie check on Transaction - Error
3. SqlTransaction has completed
4. http://forums.asp.net/t/1579684.aspx/1
5. "This SqlTransaction has completed; it is no longer usable."... configuration error?
6. dotnet.sys-con.com - SqlClient Connection Pooling Exposed
7. Thread abort leaves zombie transactions and broken SqlConnection

---

Answer 1

You should leave some of the work to compiler, to wrap that in a try/catch/finally for you.

Also, you should expect that Rollback can occasionally throw an exception, if a problem occurs in Commit stage, or if a connection to server breaks. For that reason you should wrap it in a try/catch.

try
{
    transaction.Rollback();
}
catch (Exception ex2)
{
    // This catch block will handle any errors that may have occurred 
    // on the server that would cause the rollback to fail, such as 
    // a closed connection.
    Console.WriteLine("Rollback Exception Type: {0}", ex2.GetType());
    Console.WriteLine("  Message: {0}", ex2.Message);
}

This is copied exactly from MSDN documentation page for Rollback method.

I see that you're worried that you have a zombie transaction. In case you pasted, it doesn't sound like you have a problem. You're transaction has been completed, and you should no longer have anything to do with it. Remove references to it if you hold them, and forget about it.

---

From MSDN - SqlTransaction.Rollback Method

A Rollback generates an InvalidOperationException if the connection is terminated or if the transaction has already been rolled back on the server.

Rethrow a new exception to tell user that data may not have been saved, and ask her to refresh and review

Answer 2

Note: This error came only once.

then it is very hard to say much; it could be simply that the // Other Code etc simply took to long, and the entire thing got killed. Maybe your connection died, or an admin deliberately killed it because you were blocking.

What is the mistake in the code?

over-complicating it; it can be much simpler:

using (var connection = new SqlConnection(connectionString))
{
    connection.Open();
    using(var transaction = connection.BeginTransaction())
    {
        try
        {
            sessionID = GetSessionIDForAssociate(connection, empID, transaction);
            //Other Code
            transaction.Commit();
         }
         catch
         {
            transaction.Rollback();
            throw;
         }
    }
}

much less code to get wrong.

Answer 3

I use code below can reproduce this error, I use 1000 tasks to execute Sql, after about 300 tasks Successfully Completed, lots of exception about timeout error start to occur on ExecuteNonQuery(),

then next error This SqlTransaction has completed will occur on transaction.RollBack(); and its call stack also contains ZombieCheck().

(If single program with 1000 tasks pressure not enough, you can execute multiple compiled exe file at the same time, or even use multi computers execute to one DataBase.)

So I guess one of the reason cause this error can be something wrong in Connection, then cause the transaction error happens as well.

Task[] tasks = new Task[1000];
for (int i = 0; i < 1000; i++)
{
    int j = i;
    tasks[i] = new Task(() =>
         ExecuteSqlTransaction("YourConnectionString", j)
        );
}

foreach (Task task in tasks)
{
    task.Start();
}       

/////////////    

public void ExecuteSqlTransaction(string connectionString, int exeSqlCou)
{

    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        connection.Open();

        SqlCommand command = connection.CreateCommand();
        SqlTransaction transaction;

        // Start a local transaction.
        transaction = connection.BeginTransaction();

        // Must assign both transaction object and connection
        // to Command object for a pending local transaction
        command.Connection = connection;
        command.Transaction = transaction;

        try
        {
            command.CommandText =
                "select * from Employee";
            command.ExecuteNonQuery();

            // Attempt to commit the transaction.
            transaction.Commit();

            Console.WriteLine("Execute Sql to database."
                + exeSqlCou);
        }
        catch (Exception ex)
        {
            Console.WriteLine("Commit Exception Type: {0}", ex.GetType());
            Console.WriteLine("  Message: {0}", ex.Message);


            // Attempt to roll back the transaction.
            try
            {
                transaction.Rollback();
            }
            catch (Exception ex2)
            {
                // This catch block will handle any errors that may have occurred
                // on the server that would cause the rollback to fail, such as
                // a closed connection.
                Console.WriteLine("Rollback Exception Type: {0}", ex2.GetType());
                Console.WriteLine("  Message: {0}", ex2.Message);

            }
        }
    }
}

Besides I find if I commit twice sequentailly will invoke this exception as well.

       transaction.Commit();
       transaction.Commit();

Or if Connection Closed before commit also invoke this error.

       connection.Close();
       transaction.Commit();

Update:

I find it strange that I create another new table and insert 500 thousand data to it,

then use 100000 tasks with select * from newtable sql, running 5 programs at the same time, this time the Timeout Error occur, but when transaction.Rollback() it didn't invoke the SQLTransaction has completed error.

but if the Timeout Error occur, jump into the catch block, and in the catch block do transaction.Commit() again, the SQLTransaction has completed error will happen.

Answer 4

I have experienced this error once and i was stuck and unable to know what is going wrong. Actually i was deleting a record and in the Stored procedure i was not deleting its child and specially the delete statement in Stored Procedure was inside the Transaction boundary. I removed that transaction code from stored procedure and got rid of getting this Error of “This SqlTransaction has completed; it is no longer usable.”

Answer 5

This message is simply because that you wrote code that throws an exception after the transaction has been already committed successfully.Please try to check the code you wrote after the Commit method or you can handle it by using Try..Catch and finally Blocks :) .