code: protected Enumeration cleanUpCache(long now) {
          //create local variable - JIT performance improvement
          final boolean isTraceOn = com.ibm.websphere.ras.TraceComponent.isAnyTracingEnabled();
          if (isTraceOn && LoggingUtil.SESSION_LOGGER_WAS.isLoggable(Level.FINER)) {
              LoggingUtil.SESSION_LOGGER_WAS.entering(methodClassName, methodNames[CLEAN_UP_CACHE]);
          }
  
          Vector timedOutSessions = new Vector();
  
          Enumeration sessionIds = tableKeys();
          while (sessionIds.hasMoreElements()) {
              String id = (String) sessionIds.nextElement();
              BackedSession backedSess = (BackedSession) superGet(id);
  
              if (backedSess != null) {
                  try {
                      if (hasTimedOut(backedSess, now)) {
                          if (isTraceOn && LoggingUtil.SESSION_LOGGER_WAS.isLoggable(Level.FINE)) {
                              LoggingUtil.SESSION_LOGGER_WAS.logp(Level.FINE, methodClassName, methodNames[CLEAN_UP_CACHE], "adding to inval list " + backedSess.getId());
                          }
                          timedOutSessions.addElement(backedSess.getId());
                      }
  
                  } catch (Throwable t) {
                      com.ibm.ws.ffdc.FFDCFilter.processException(t, "com.ibm.ws.session.store.common.BackedHashMap.cleanUpCache", "951", backedSess);
                      timedOutSessions.addElement(backedSess.getId());
                  }
              }
          }
  
          Enumeration timedOutEnum = timedOutSessions.elements();
          handleDiscardedCacheItems(timedOutEnum);
          if (isTraceOn && LoggingUtil.SESSION_LOGGER_WAS.isLoggable(Level.FINER)) {
              LoggingUtil.SESSION_LOGGER_WAS.exiting(methodClassName, methodNames[CLEAN_UP_CACHE], timedOutSessions.elements());
          }
          return timedOutSessions.elements();
      }
docs: /*
  cleanUpCache