When a connection is operating in implicit transaction mode, the instance of the SQL Server Database Engine automatically starts a new transaction after the current transaction is committed or rolled back. You do nothing to delineate the start of a transaction; you only commit or roll back each transaction. Implicit transaction mode generates a continuous chain of transactions.
After implicit transaction mode has been set on for a connection, the instance of the Database Engine automatically starts a transaction when it first executes any of these statements:
The transaction remains in effect until you issue a COMMIT or ROLLBACK statement. After the first transaction is committed or rolled back, the instance of the Database Engine automatically starts a new transaction the next time any of these statements is executed by the connection. The instance keeps generating a chain of implicit transactions until implicit transaction mode is turned off.
Implicit transaction mode is set either using the Transact-SQL SET statement, or through database API functions and methods.
Under a multiple active result sets (MARS) session, a Transact-SQL implicit transaction becomes a batch-scoped transaction. If the batch-scoped transaction is not committed or rolled back when the batch completes, SQL Server automatically rolls back the transaction. For more information, see Controlling Transactions (Database Engine) and Transaction Statements (Transact-SQL).