code: @Override
      protected boolean performDialogOperation() throws CmsException {
  
          //on multi resource operation display "please wait" screen
          if (isMultiOperation() && !DIALOG_WAIT.equals(getParamAction())) {
              return false;
          }
          // determine action to perform (lock, unlock, change lock)
          int dialogAction = getDialogAction(getCms());
  
          // now perform the operation on the resource(s)
          Iterator<String> i = getResourceList().iterator();
          while (i.hasNext()) {
              String resName = i.next();
              try {
                  performSingleResourceOperation(resName, dialogAction);
              } catch (CmsException e) {
                  // collect exceptions to create a detailed output
                  addMultiOperationException(e);
              }
          }
          // generate the error message for exception
          String message;
          if (dialogAction == TYPE_LOCK) {
              message = Messages.ERR_LOCK_MULTI_0;
          } else {
              message = Messages.ERR_UNLOCK_MULTI_0;
          }
          checkMultiOperationException(Messages.get(), message);
  
          return true;
      }
docs: Performs the lock/unlock/steal lock operation.<p>
  
  @return true, if the operation was performed, otherwise false
  @throws CmsException if operation is not successful