code: public void rollback() throws HandlerException {
          if (_isInitiator) {
              try {
                  _userTx.rollback();
              } catch (SystemException se) {
                  throw CommonKnowledgeMessages.MESSAGES.userTransactionRollbackFailed(se);
              }
          } else if (_userTx != null) {
              try {
                  _userTx.setRollbackOnly();
              } catch (SystemException se) {
                  throw CommonKnowledgeMessages.MESSAGES.userTransactionSetRollbackOnlyFailed(se);
              }
          }
      }
docs: Rollback.
  
  @throws HandlerException oops