code: private void createServantRoutingAffinity() throws BeanNotReentrantException {
          if (!ivServantRoutingAffinity && container.ivStatefulBeanEnqDeq != null) {
              StatefulSessionKey sskey = (StatefulSessionKey) beanId.getPrimaryKey();
              byte[] pKeyBytes = sskey.getBytes();
  
              int retcode = container.ivStatefulBeanEnqDeq.SSBeanEnq(pKeyBytes, !home.beanMetaData.sessionActivateTran, true);
              if (retcode != 0) {
                  if (TraceComponent.isAnyTracingEnabled() && tc.isEventEnabled())
                      Tr.event(tc, "Could not ENQ session bean with key = " + sskey);
                  throw new BeanNotReentrantException("Could not ENQ session bean with key = " + sskey);
              }
  
              ivServantRoutingAffinity = true;
          }
      }
docs: Creates a routing affinity for this bean on the current servant. This
  method should only be called on z/OS.