Receive 500 error in Load test of weblogic - performance

Question

I try to load test an ADF web site that deployed on a Weblogic server with WPLT 6.6 . when I Replay single transaction, everything is OK and also when I try to load test for one user everything is OK, but when the second concurrent user enter the test, the server response with 500 error (validation). I do not know what is the problem.
welogic's log :
####<Jul 11, 2017 10:48:16 AM IRDT> <Info> <DiagnosticsWatch> <APP-EGOV> <EBOX_MNGS02> <[ACTIVE] ExecuteThread: '12' for queue: 'weblogic.kernel.Default (self-tuning)'> <<WLS Kernel>> <> <3992c89e-704b-431b-8d6d-3e5db34763d3-000025c7> <1499753896280> <[severity-value: 64] [rid: 0] [partition-id: 0] [partition-name: DOMAIN] > <BEA-320204> <Executing action FMWDFW-notification with timeout period 0 seconds.>
####<Jul 11, 2017 10:48:57 AM IRDT> <Error> <HTTP> <APP-EGOV> <EBOX_MNGS02> <[ACTIVE] ExecuteThread: '1' for queue: 'weblogic.kernel.Default (self-tuning)'> <<WLS Kernel>> <> <3992c89e-704b-431b-8d6d-3e5db34763d3-000027cf> <1499753937625> <[severity-value: 8] [rid: 0] [partition-id: 0] [partition-name: DOMAIN] > <BEA-101020> <[ServletContext#142750200[app:EboxInboxApp module:Inbox path:null spec-version:3.1]] Servlet failed with an Exception
java.lang.RuntimeException: An attempt has been made to update the immutable value associated with parameter DSID in context 3992c89e-704b-431b-8d6d-3e5db34763d3-000027cf,0. The parameter is not updateable.
at oracle.dms.context.internal.wls2.WLS2ExecutionContext.setValueAccordingToDescriptor(WLS2ExecutionContext.java:639)
at oracle.dms.context.ExecutionContext.setValue(ExecutionContext.java:1021)
at oracle.dms.servlet.DMSServletFilter.doFilter(DMSServletFilter.java:211)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:78)
at weblogic.servlet.internal.RequestEventsFilter.doFilter(RequestEventsFilter.java:32)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:78)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.wrapRun(WebAppServletContext.java:3654)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:3620)
at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:326)
at weblogic.security.service.SecurityManager.runAsForUserCode(SecurityManager.java:196)
at weblogic.servlet.provider.WlsSecurityProvider.runAsForUserCode(WlsSecurityProvider.java:203)
at weblogic.servlet.provider.WlsSubjectHandle.run(WlsSubjectHandle.java:71)
at weblogic.servlet.internal.WebAppServletContext.doSecuredExecute(WebAppServletContext.java:2423)
at weblogic.servlet.internal.WebAppServletContext.securedExecute(WebAppServletContext.java:2280)
at weblogic.servlet.internal.WebAppServletContext.execute(WebAppServletContext.java:2258)
at weblogic.servlet.internal.ServletRequestImpl.runInternal(ServletRequestImpl.java:1626)
at weblogic.servlet.internal.ServletRequestImpl.run(ServletRequestImpl.java:1586)
at weblogic.servlet.provider.ContainerSupportProviderImpl$WlsRequestExecutor.run(ContainerSupportProviderImpl.java:270)
at weblogic.invocation.ComponentInvocationContextManager._runAs(ComponentInvocationContextManager.java:348)
at weblogic.invocation.ComponentInvocationContextManager.runAs(ComponentInvocationContextManager.java:333)
at weblogic.work.LivePartitionUtility.doRunWorkUnderContext(LivePartitionUtility.java:54)
at weblogic.work.PartitionUtility.runWorkUnderContext(PartitionUtility.java:41)
at weblogic.work.SelfTuningWorkManagerImpl.runWorkUnderContext(SelfTuningWorkManagerImpl.java:617)
at weblogic.work.ExecuteThread.execute(ExecuteThread.java:397)
at weblogic.work.ExecuteThread.run(ExecuteThread.java:346)
>
####<Jul 11, 2017 10:48:57 AM IRDT> <Notice> <Diagnostics> <APP-EGOV> <EBOX_MNGS02> <[STANDBY] ExecuteThread: '7' for queue: 'weblogic.kernel.Default (self-tuning)'> <<WLS Kernel>> <> <3992c89e-704b-431b-8d6d-3e5db34763d3-000027d8> <1499753937628> <[severity-value: 32] [rid: 0] [partition-id: 0] [partition-name: DOMAIN] > <BEA-320068> <Watch "UncheckedException" in module "Module-FMWDFW" with severity "Notice" on server "EBOX_MNGS02" has triggered at Jul 11, 2017 10:48:57 AM IRDT. Notification details:
WatchRuleType: Log
WatchRule: (SEVERITY = 'Error') AND ((MSGID = 'WL-101020') OR (MSGID = 'WL-101017') OR (MSGID = 'WL-000802') OR (MSGID = 'BEA-101020') OR (MSGID = 'BEA-101017') OR (MSGID = 'BEA-000802'))
WatchData: MESSAGE = [ServletContext#142750200[app:EboxInboxApp module:Inbox path:null spec-version:3.1]] Servlet failed with an Exception
java.lang.RuntimeException: An attempt has been made to update the immutable value associated with parameter DSID in context 3992c89e-704b-431b-8d6d-3e5db34763d3-000027cf,0. The parameter is not updateable.
at oracle.dms.context.internal.wls2.WLS2ExecutionContext.setValueAccordingToDescriptor(WLS2ExecutionContext.java:639)
at oracle.dms.context.ExecutionContext.setValue(ExecutionContext.java:1021)
at oracle.dms.servlet.DMSServletFilter.doFilter(DMSServletFilter.java:211)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:78)
at weblogic.servlet.internal.RequestEventsFilter.doFilter(RequestEventsFilter.java:32)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:78)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.wrapRun(WebAppServletContext.java:3654)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:3620)
at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:326)

Answer 1

Here is the most common cause of an HTTP 500 during a performance test
Failure to check every request for a positive expected result (not just HTTP 200) and then a failure to branch the code when an unexpected result occurs. The HTTP 500 then occurs one or two steps down the line past the point where the valid HTTP 200 request response with the unexpected response content appears. The end result is that the next (or possibly next next) request is out of context with the state of the business process. As an unhandled exception from development (because a natural user would not be able to progress) an HTTP 500 results.
As to why the business process has come off the rails? The reasons are multitude. You could have some unhandled dynamic data related to session, state, time, security tokens, user credentials, business process data/keys, etc... You may have data which is in a different state that what is needed for the business process, such as trying to re-use, use-once data. You may even have someone else changing the state of your data during your test if you share your environment and test data with other groups at the same time.
If you are not actively checking in your test code for a positive, expected condition with each test step (test 101 stuff) then what you are doing is "throwing load" and these types of HTTP 500 errors should be expected and common.