This function is called when local transaction starts.

0: transaction ID stored, transaction can be started.

1: transaction already done, skip the request.

< 0: cannot lock transaction, internal error.

transID: The transaction ID for the local transaction.

This function is a pure virtual function to be implemented by derived classes. It is called when a local transaction is starting. Since a transactional RFC call can be issued many times by the client system, the function is responsible for storing the transaction ID in permanent storage. If the client system tries starting the same transaction a second time, the function has to return 1.

Do not call this function yourself, it is automatically invoked during Run.