ADFC-00024-oracle.adf.controller.ControllerException:: No ExternalContext could be found.

 ADFC-00024- No ExternalContext could be found.
this is the exception, i have faced while working on my new ADF application and due to this exception application crashed(Internal Server Error-500)
After lot of googling and searching on OTN, i found a solution for this exception- but really don't understand that how it works-
log of ADFC-00024 problem-

 oracle.adf.controller.ControllerException: ADFC-00024: No ExternalContext could be found.  
      at oracle.adfinternal.controller.util.JsfInterfaceImpl.getExternalContext(JsfInterfaceImpl.java:394)  
      at oracle.adfinternal.controller.util.JsfInterfaceImpl.getRequestMap(JsfInterfaceImpl.java:143)  
      at oracle.adfinternal.controller.state.AdfcContext.getCurrentInstance(AdfcContext.java:219)  
      at oracle.adfinternal.controller.ControllerContextImpl.getViewPortByClientId(ControllerContextImpl.java:121)  
      at oracle.adf.controller.internal.binding.DCTaskFlowBinding.getGuardingPermission(DCTaskFlowBinding.java:204)  
      at oracle.adf.model.binding.DCBindingContainer.getGuardingPermission(DCBindingContainer.java:3849)  
      at oracle.adf.model.binding.DCBindingContainer.internalIsViewable(DCBindingContainer.java:3855)  
      at oracle.adf.model.binding.DCBindingContainer.isViewable(DCBindingContainer.java:3826)  
      at oracle.adf.model.binding.DCBindingContainer.resetSuspendedExecutables(DCBindingContainer.java:3490)  
      at oracle.adf.model.binding.DCBindingContainer.resetSuspendedExecutables(DCBindingContainer.java:3492)  
      at oracle.adf.model.binding.DCBindingContainer.internalRefreshControl(DCBindingContainer.java:3365)  
      at oracle.adf.model.binding.DCBindingContainer.refresh(DCBindingContainer.java:2911)  
      at oracle.adf.controller.v2.lifecycle.PageLifecycleImpl.prepareModel(PageLifecycleImpl.java:115)  
      at oracle.adf.controller.v2.lifecycle.Lifecycle$2.execute(Lifecycle.java:149)  
      at oracle.adfinternal.controller.lifecycle.LifecycleImpl.executePhase(LifecycleImpl.java:197)  
      at oracle.adfinternal.controller.faces.lifecycle.ADFPhaseListener.access$400(ADFPhaseListener.java:23)  
      at oracle.adfinternal.controller.faces.lifecycle.ADFPhaseListener$PhaseInvokerImpl.startPageLifecycle(ADFPhaseListener.java:238)  
      at oracle.adfinternal.controller.faces.lifecycle.ADFPhaseListener$1.after(ADFPhaseListener.java:274)  
      at oracle.adfinternal.controller.faces.lifecycle.ADFPhaseListener.afterPhase(ADFPhaseListener.java:75)  
      at oracle.adfinternal.controller.faces.lifecycle.ADFLifecyclePhaseListener.afterPhase(ADFLifecyclePhaseListener.java:53)  
      at oracle.adfinternal.view.faces.lifecycle.LifecycleImpl._executePhase(LifecycleImpl.java:439)  
      at oracle.adfinternal.view.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:204)  
      at javax.faces.webapp.FacesServlet.service(FacesServlet.java:312)  
      at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:227)  
      at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:125)  
      at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:300)  
      at weblogic.servlet.internal.TailFilter.doFilter(TailFilter.java:26)  
      at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)  
      at oracle.adf.model.servlet.ADFBindingFilter.doFilter(ADFBindingFilter.java:173)  
      at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)  
      at oracle.adfinternal.view.faces.webapp.rich.RegistrationFilter.doFilter(RegistrationFilter.java:122)  
      at org.apache.myfaces.trinidadinternal.webapp.TrinidadFilterImpl$FilterListChain.doFilter(TrinidadFilterImpl.java:468)  
      at oracle.adfinternal.view.faces.activedata.AdsFilter.doFilter(AdsFilter.java:60)  
      at org.apache.myfaces.trinidadinternal.webapp.TrinidadFilterImpl$FilterListChain.doFilter(TrinidadFilterImpl.java:468)  
      at org.apache.myfaces.trinidadinternal.webapp.TrinidadFilterImpl._doFilterImpl(TrinidadFilterImpl.java:293)  
      at org.apache.myfaces.trinidadinternal.webapp.TrinidadFilterImpl.doFilter(TrinidadFilterImpl.java:199)  
      at org.apache.myfaces.trinidad.webapp.TrinidadFilter.doFilter(TrinidadFilter.java:92)  
      at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)  
      at oracle.adf.library.webapp.LibraryFilter.doFilter(LibraryFilter.java:180)  
      at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)  
      at oracle.security.jps.ee.http.JpsAbsFilter$1.run(JpsAbsFilter.java:111)  
      at java.security.AccessController.doPrivileged(Native Method)  
      at oracle.security.jps.util.JpsSubject.doAsPrivileged(JpsSubject.java:313)  
      at oracle.security.jps.ee.util.JpsPlatformUtil.runJaasMode(JpsPlatformUtil.java:413)  
      at oracle.security.jps.ee.http.JpsAbsFilter.runJaasMode(JpsAbsFilter.java:94)  
      at oracle.security.jps.ee.http.JpsAbsFilter.doFilter(JpsAbsFilter.java:161)  
      at oracle.security.jps.ee.http.JpsFilter.doFilter(JpsFilter.java:71)  
      at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)  
      at oracle.dms.servlet.DMSServletFilter.doFilter(DMSServletFilter.java:136)  
      at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)  
      at weblogic.servlet.internal.RequestEventsFilter.doFilter(RequestEventsFilter.java:27)  
      at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)  
      at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.wrapRun(WebAppServletContext.java:3715)  
      at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:3681)  
      at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)  
      at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:120)  
      at weblogic.servlet.internal.WebAppServletContext.securedExecute(WebAppServletContext.java:2277)  
      at weblogic.servlet.internal.WebAppServletContext.execute(WebAppServletContext.java:2183)  
      at weblogic.servlet.internal.ServletRequestImpl.run(ServletRequestImpl.java:1454)  
      at weblogic.work.ExecuteThread.execute(ExecuteThread.java:209)  
      at weblogic.work.ExecuteThread.run(ExecuteThread.java:178)  

In my case this was due to Application Module configuration, in adf application we have two configuration .

1. AMLocal
2. AMShared

For local configuration ,in Pooling and Scalability there is Maximum Pool Size is 4096 but for shared it is only 1
i am not getting why this is so, then i have set Maximum Pool Size for shared configuration to 4096 and it is working-