code: public void begin() throws HandlerException {
          if (_enabled) {
              try {
                  _userTx = TransactionManagerLocator.INSTANCE.getUserTransaction();
                  if (_userTx.getStatus() == Status.STATUS_NO_TRANSACTION) {
                      _userTx.begin();
                      _isInitiator = true;
                  }
              } catch (SystemException se) {
                  throw CommonKnowledgeMessages.MESSAGES.userTransactionBeginFailedSystem(se);
              } catch (NotSupportedException nse) {
                  throw CommonKnowledgeMessages.MESSAGES.userTransactionBeginFailedNSE(nse);
              }
          }
      }
docs: Begin.
  
  @throws HandlerException oops