We found have error at A server with a 13c's agent and the number of occurrences is frequent.

we found error informations from  the gcagent_erro.log file.

oracle.sysman.gcagent.task.TaskZombieException: task declared as a zombie
    at oracle.sysman.gcagent.task.TaskFutureImpl$WrappedTask.accountedCall(TaskFutureImpl.java:621)
    at oracle.sysman.gcagent.task.TaskFutureImpl$WrappedTask.call(TaskFutureImpl.java:644)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at oracle.sysman.gcagent.task.TaskFutureImpl.run1(TaskFutureImpl.java:373)
    at oracle.sysman.gcagent.task.TaskFutureImpl.run(TaskFutureImpl.java:330)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at oracle.sysman.gcagent.task.executor.TrackThreadFactory$1.run(TrackThreadFactory.java:54)
    atoracle.sysman.gcagent.util.system.GCAThread$RunnableWrapper.run(GCAThread.java:198)
    at java.lang.Thread.run(Thread.java:745)
2017-02-16 15:30:01,734 [2713889:GC.Executor.124190
(oracle_database:hpaypr1:Response)] ERROR - oracle_database:hpaypr1:Response
oracle.sysman.gcagent.task.TaskZombieException: task declared as a zombie
    at oracle.sysman.gcagent.task.TaskFutureImpl$WrappedTask.accountedCall(TaskFutureImpl.java:621)
    at oracle.sysman.gcagent.task.TaskFutureImpl$WrappedTask.call(TaskFutureImpl.java:644)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at oracle.sysman.gcagent.task.TaskFutureImpl.run1(TaskFutureImpl.java:373)
    at oracle.sysman.gcagent.task.TaskFutureImpl.run(TaskFutureImpl.java:330)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at oracle.sysman.gcagent.task.executor.TrackThreadFactory$1.run(TrackThreadFactory.java:54)
    at oracle.sysman.gcagent.util.system.GCAThread$RunnableWrapper.run(GCAThread.java:198)
    at java.lang.Thread.run(Thread.java:745)

CAUSE:
When an agent task such as collecting metrics is running more than the expected time, the process is marked as Zombie.
This generates an Incident in order to let the Enterprise Manager (EM) Administrator know that a task has generated a zombie process.
The zombie process is a valid mechanism of the agent.
A parameter to eliminate Incident creation for Zombies needs to be added to the $AGENT_INST/sysman/config/emd.properties. 
This parameter was not documented; and a bug was filed.

TECHNICAL IMPACT
1.Zombie processes and Incidents created. 
2.Agent can try to restart
 
RELATED ISSUES (bugs, forums, RFAs)
similar to bug : Bug 22221528 – Zombie process seen during DB Metric collection

SOLUTION:
In order to avoid the Zombie Process Alerts/Incidents, the following parameter can be added to the $AGENT_INST/sysman/config/emd.properties:

_zombieCreateIncident=false 

1. Edit the file emd.properties
2. Add the parameter : _zombieCreateIncident=false
3. emctl stop agent
4. emctl start agent

Other parameter reference:
_canceledThreadWait == > The amount of time before a canceled thread is considered a 'zombie' thread
_zombieSuspensions ==> Whether to indefinitely suspend a zombie task
_zombieThreadPercentThreshold ==> The number of 'zombie' threads (as a percent of the REGULAR thread pool) before a bounce will be started; set to zero to disable auto restarts
Note: Setting these parameters , agent restart due to zombies would reduce/stop and incident  dump shall get created
_zombieCreateIncident==>Whether to create an incident for the zombie abort

13cR2 Modify OMS HTTPS and HTTP Console And Upload Ports After 13c Cloud Control Installation

Cause：
The port is occupied, "em13c" directory had moved,but the process still active:

[oracle@trsen:/u01/app/em13cR2/middle/bin]$netstat -apn | grep 7802
(Not all processes could be identified, non-owned process info
 will not be shown, you would have to be root to see it all.)
tcp        0      0 :::7802                     :::*                        LISTEN      6986/httpd.worker   
[oracle@trsen:/u01/app/em13cR2/middle/bin]$ps -aux | grep 6986
Warning: bad syntax, perhaps a bogus '-'? See /usr/share/doc/procps-3.2.8/FAQ
oracle    3893  0.0  5.4 4016748 669868 ?      Ss   Nov10   0:40 ora_p006_EMREP
oracle    6986  0.0  0.0 1998880  644 ?        Sl   Nov11   0:07 /u01/app/em13c/middleware/ohs/bin/httpd.worker -k start -f /u01/app/em13c/gc_inst/user_projects/domains/GCDomain/config/fmwconfig/components/OHS/instances/ohs1/httpd.conf

Solution：
1.lists the current value of the https/http console/upload ports informations are followed:
Now port for oms:
HTTP Console Port          : 7790
HTTPS Console Port         : 7803
HTTP Upload Port           : 4890
HTTPS Upload Port          : 4904

we modify port to new port:
HTTP Console Port          : 7788
HTTPS Console Port         : 7802
HTTP Upload Port           : 4889
HTTPS Upload Port          : 4903

OMS property of ports:
HTTPS CONSOLE PORT:oracle.sysman.emSDK.svlt.EMConsoleServerHTTPSPort
HTTPS UPLOAD PORT:oracle.sysman.emSDK.svlt.ConsoleServerHTTPSPort
HTTP CONSOLE PORT:oracle.sysman.emSDK.svlt.EMConsoleServerPort
HTTP UPLOAD PORT:oracle.sysman.emSDK.svlt.ConsoleServerPort

Changing HTTPS console port:
1. Verify the existing https console port:

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl get property -name  oracle.sysman.emSDK.svlt.EMConsoleServerHTTPSPort -sysman_pwd em13c09
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Value for property oracle.sysman.emSDK.svlt.EMConsoleServerHTTPSPort for oms trsen.em13c.cn:4890_Management_Service is 7803

2. Stop the OMS

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl stop oms
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Stopping Oracle Management Server...
Oracle Management Server Successfully Stopped
Oracle Management Server is Down
JVMD Engine is Down

3.Change the https console port

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl set property -name oracle.sysman.emSDK.svlt.EMConsoleServerHTTPSPort -value 7802 -sysman_pwd em13c09
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Property oracle.sysman.emSDK.svlt.EMConsoleServerHTTPSPort for oms trsen.em13c.cn:4890_Management_Service has been set to value 7802
OMS restart is required to reflect the new property value

4.Take a backup of file and update ssl.conf and emgc.properties :

[oracle@trsen:/u01/app/em13cR2/gc_inst/user_projects/domains/GCDomain/config/fmwconfig/components/OHS/ohs1]$cat ssl.conf | grep 7803
Listen 7803 #OHS_SSL_PORT
<VirtualHost *:7803> #OHS_SSL_VH

[oracle@trsen:/u01/app/em13cR2/gc_inst/user_projects/domains/GCDomain/config/fmwconfig/components/OHS/ohs1]$cat ssl.conf | grep 7802
Listen 7802 #OHS_SSL_PORT
<VirtualHost *:7802> #OHS_SSL_VH

[oracle@trsen:/u01/app/em13cR2/gc_inst/em/EMGC_OMS1]$cat emgc.properties | grep 7803
EM_CONSOLE_HTTPS_PORT=7803

[oracle@trsen:/u01/app/em13cR2/gc_inst/em/EMGC_OMS1]$cat emgc.properties | grep 7802
EM_CONSOLE_HTTPS_PORT=7802

5.restart oms:

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl stop oms -all -force
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Stopping Oracle Management Server...
WebTier Successfully Stopped
Oracle Management Server Already Stopped
Oracle Management Server is Down
JVMD Engine is Down
BI Publisher is disabled, to enable BI Publisher on this host, use the 'emctl config oms -enable_bip' command
Stopping BI Publisher Server...
BI Publisher Server Already Stopped
BI Publisher is disabled, to enable BI Publisher on this host, use the 'emctl config oms -enable_bip' command
AdminServer Successfully Stopped
BI Publisher Server is Down
BI Publisher is disabled, to enable BI Publisher on this host, use the 'emctl config oms -enable_bip' command

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl start oms
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Starting Oracle Management Server...
WebTier Successfully Started
Oracle Management Server Successfully Started
Oracle Management Server is Up
JVMD Engine is Up

Changing HTTPS Upload Port
1. Verify the OMS HTTPS upload port:

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl get property -name oracle.sysman.emSDK.svlt.ConsoleServerHTTPSPort -sysman_pwd em13c09
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Value for property oracle.sysman.emSDK.svlt.ConsoleServerHTTPSPort for oms trsen.em13c.cn:4890_Management_Service is 4904

2. Modify the HTTPS upload port to new value:

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl set property -name oracle.sysman.emSDK.svlt.ConsoleServerHTTPSPort -value 4903 -sysman_pwd em13c09
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Property oracle.sysman.emSDK.svlt.ConsoleServerHTTPSPort for oms trsen.em13c.cn:4890_Management_Service has been set to value 4903
OMS restart is required to reflect the new property value

3. Take a backup of the file and update emgc.properties and httpd_em.conf(have two places) file:

[oracle@trsen:/u01/app/em13cR2/gc_inst/em/EMGC_OMS1]$cat emgc.properties | grep 4904
EM_UPLOAD_HTTPS_PORT=4904
[oracle@trsen:/u01/app/em13cR2/gc_inst/em/EMGC_OMS1]$cat emgc.properties | grep 4903
EM_UPLOAD_HTTPS_PORT=4903

[oracle@trsen:/u01/app/em13cR2/gc_inst/user_projects/domains/GCDomain/config/fmwconfig/components/OHS/instances/ohs1/moduleconf]$cat httpd_em.conf | grep 4904
    Listen 4904
    <VirtualHost *:4904>
[oracle@trsen:/u01/app/em13cR2/gc_inst/user_projects/domains/GCDomain/config/fmwconfig/components/OHS/instances/ohs1/moduleconf]$cat httpd_em.conf | grep 4903
    Listen 4903
    <VirtualHost *:4903>

[oracle@trsen:/u01/app/em13cR2/gc_inst/user_projects/domains/GCDomain/config/fmwconfig/components/OHS/ohs1/moduleconf]$cat httpd_em.conf | grep 4904
    Listen 4904
    <VirtualHost *:4904>
[oracle@trsen:/u01/app/em13cR2/gc_inst/user_projects/domains/GCDomain/config/fmwconfig/components/OHS/ohs1/moduleconf]$cat httpd_em.conf | grep 4903
    Listen 4903
    <VirtualHost *:4903>

4. Restart OMS:

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl stop oms -force -all
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Stopping Oracle Management Server...
WebTier Successfully Stopped
Oracle Management Server Successfully Stopped
Oracle Management Server is Down
JVMD Engine is Down
BI Publisher is disabled, to enable BI Publisher on this host, use the 'emctl config oms -enable_bip' command
Stopping BI Publisher Server...
BI Publisher Server Already Stopped
BI Publisher is disabled, to enable BI Publisher on this host, use the 'emctl config oms -enable_bip' command
AdminServer Successfully Stopped
BI Publisher Server is Down
BI Publisher is disabled, to enable BI Publisher on this host, use the 'emctl config oms -enable_bip' command

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl start oms
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Starting Oracle Management Server...
WebTier Successfully Started
Oracle Management Server Successfully Started
Oracle Management Server is Up
JVMD Engine is Up

NOTE:
If agents are configured with https upload port then perform the following on agent machines to reflect the new OMS https upload port:
1. Take a backup of <AGENT_INST_HOME>/sysman/config/emd.properties file
2. Edit the <AGENT_INST_HOME>/sysman/config/emd.properties file as below:
REPOSITORY_URL=https://omsmachine.domain.com:4903/empbs/upload
emdWalletSrcUrl=https://omsmachine.domain.com:4903/em/wallets/emd
3. Restart the agent:
<AGENT_INST_HOME>/bin>./emctl stop agent
<AGENT_INST_HOME>/bin>./emctl start agent

Changing HTTP console port
1. Verify the OMS HTTP console port:

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl get property -name oracle.sysman.emSDK.svlt.EMConsoleServerPort -sysman_pwd em13c09
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Value for property oracle.sysman.emSDK.svlt.EMConsoleServerPort for oms trsen.em13c.cn:4890_Management_Service is 7790

2. Modify the HTTPS upload port to new value:

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl set property -name oracle.sysman.emSDK.svlt.EMConsoleServerPort -value 7788 -sysman_pwd em13c09
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Property oracle.sysman.emSDK.svlt.EMConsoleServerPort for oms trsen.em13c.cn:4890_Management_Service has been set to value 7788
OMS restart is required to reflect the new property value

3. Take a backup of the file and update emgc.properties and httpd.conf file:

[oracle@trsen:/u01/app/em13cR2/gc_inst/em/EMGC_OMS1]$cat emgc.properties | grep 7790
EM_CONSOLE_HTTP_PORT=7790 
[oracle@trsen:/u01/app/em13cR2/gc_inst/em/EMGC_OMS1]$cat emgc.properties | grep 7788
EM_CONSOLE_HTTP_PORT=7788

[oracle@trsen:/u01/app/em13cR2/gc_inst/user_projects/domains/GCDomain/config/fmwconfig/components/OHS/ohs1]$cat httpd.conf | grep 7790
Listen 7790   #OHS_LISTEN_PORT
[oracle@trsen:/u01/app/em13cR2/gc_inst/user_projects/domains/GCDomain/config/fmwconfig/components/OHS/ohs1]$cat httpd.conf | grep 7788
Listen 7788   #OHS_LISTEN_PORT

4. Restart OMS:

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl stop oms -all -force
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Stopping Oracle Management Server...
WebTier Successfully Stopped
Oracle Management Server Successfully Stopped
Oracle Management Server is Down
JVMD Engine is Down
BI Publisher is disabled, to enable BI Publisher on this host, use the 'emctl config oms -enable_bip' command
Stopping BI Publisher Server...
BI Publisher Server Already Stopped
BI Publisher is disabled, to enable BI Publisher on this host, use the 'emctl config oms -enable_bip' command
AdminServer Successfully Stopped
BI Publisher Server is Down
BI Publisher is disabled, to enable BI Publisher on this host, use the 'emctl config oms -enable_bip' command

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl start oms
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Starting Oracle Management Server...
WebTier Successfully Started
Oracle Management Server Successfully Started
Oracle Management Server is Up
JVMD Engine is Up

Changing HTTP upload port
1. Verify the OMS HTTP upload port:

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl get property -name oracle.sysman.emSDK.svlt.ConsoleServerPort -sysman_pwd em13c09
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Value for property oracle.sysman.emSDK.svlt.ConsoleServerPort for oms trsen.em13c.cn:4890_Management_Service is 4890

2. Modify the HTTP upload port to new value:

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl set property -name oracle.sysman.emSDK.svlt.ConsoleServerPort -value 4889 -sysman_pwd em13c09
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Property oracle.sysman.emSDK.svlt.ConsoleServerPort for oms trsen.em13c.cn:4890_Management_Service has been set to value 4889
OMS restart is required to reflect the new property value

3. Take a backup of the file and update /u02/em13c/gc_inst/em/EMGC_OMS1/emgc.properties file:

[oracle@trsen:/u01/app/em13cR2/gc_inst/em/EMGC_OMS1]$cat emgc.properties | grep 4890
oracle.sysman.emSDK.svlt.ConsoleServerName=trsen.em13c.cn\:4890_Management_Service
EM_UPLOAD_HTTP_PORT=4890
[oracle@trsen:/u01/app/em13cR2/gc_inst/em/EMGC_OMS1]$cat emgc.properties  | grep 4889
oracle.sysman.emSDK.svlt.ConsoleServerName=trsen.em13c.cn\:4889_Management_Service
EM_UPLOAD_HTTP_PORT=4889

[oracle@trsen:/u01/app/em13cR2/gc_inst/user_projects/domains/GCDomain/config/fmwconfig/components/OHS/ohs1/moduleconf]$cat httpd_em.conf | grep 4890
Listen 4890
<VirtualHost *:4890>
[oracle@trsen:/u01/app/em13cR2/gc_inst/user_projects/domains/GCDomain/config/fmwconfig/components/OHS/ohs1/moduleconf]$cat httpd_em.conf | grep 4889
Listen 4889
<VirtualHost *:4889>

4. Restart OMS:

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl stop oms -all -force
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Stopping Oracle Management Server...
WebTier Successfully Stopped
Oracle Management Server Successfully Stopped
Oracle Management Server is Down
JVMD Engine is Down
BI Publisher is disabled, to enable BI Publisher on this host, use the 'emctl config oms -enable_bip' command
Stopping BI Publisher Server...
BI Publisher Server Already Stopped
BI Publisher is disabled, to enable BI Publisher on this host, use the 'emctl config oms -enable_bip' command
AdminServer Successfully Stopped
BI Publisher Server is Down
BI Publisher is disabled, to enable BI Publisher on this host, use the 'emctl config oms -enable_bip' command

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl start oms
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Starting Oracle Management Server...
WebTier Successfully Started
Oracle Management Server Successfully Started
Oracle Management Server is Up
JVMD Engine is Up

NOTE:
If agents are configured with http upload port then perform the following on agent machines to reflect the new OMS http upload port:
1. Take a backup of <AGENT_INST_HOME>/sysman/config/emd.properties file
2. Edit the <AGENT_INST_HOME>/sysman/config/emd.properties file as below:
REPOSITORY_URL=http://omsmachine.domain.com:4889/empbs/upload
emdWalletSrcUrl=http://omsmachine.domain.com:4889/em/wallets/emd
3. Restart the agent:
<AGENT_INST_HOME>/bin>./emctl stop agent
<AGENT_INST_HOME>/bin>./emctl start agent

Verify OMS port informations:

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl status oms -details -sysman_pwd em13c09
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Console Server Host        : trsen.em13c.cn
HTTP Console Port          : 7788
HTTPS Console Port         : 7802
HTTP Upload Port           : 4889
HTTPS Upload Port          : 4903
EM Instance Home           : /u01/app/em13cR2/gc_inst/em/EMGC_OMS1
OMS Log Directory Location : /u01/app/em13cR2/gc_inst/em/EMGC_OMS1/sysman/log
OMS is not configured with SLB or virtual hostname
Agent Upload is unlocked.
OMS Console is unlocked.
Active CA ID: 1
Console URL: https://trsen.em13c.cn:7802/em
Upload URL: https://trsen.em13c.cn:4903/empbs/upload

WLS Domain Information
Domain Name            : GCDomain
Admin Server Host      : trsen.em13c.cn
Admin Server HTTPS Port: 7103
Admin Server is RUNNING

Oracle Management Server Information
Managed Server Instance Name: EMGC_OMS1
Oracle Management Server Instance Host: trsen.em13c.cn
WebTier is Up
Oracle Management Server is Up
JVMD Engine is Up

BI Publisher Server Information
BI Publisher Managed Server Name: BIP
BI Publisher Server is Down
BI Publisher is disabled, to enable BI Publisher on this host, use the 'emctl config oms -enable_bip' command

The error may occur when "emctl status oms -details":

2016-11-14 13:22:12,507 [main] ERROR oms.PrintOMSSetupInfo main.343 – Failed to find OMS details: null
java.lang.NullPointerException
    at oracle.sysman.emctl.util.EmctlUtil.getOMSSetupInfo(EmctlUtil.java:978)
    at oracle.sysman.emctl.oms.PrintOMSSetupInfo.main(PrintOMSSetupInfo.java:155)

solution:

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl secure oms
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Securing OMS... Started.
Enter Enterprise Manager Root (SYSMAN) Password : 
Enter Agent Registration Password : 
Securing OMS... Successful
Restart OMS

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl stop oms -all -force
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Stopping Oracle Management Server...
WebTier Successfully Stopped
Oracle Management Server Successfully Stopped
Oracle Management Server is Down
JVMD Engine is Down
BI Publisher is disabled, to enable BI Publisher on this host, use the 'emctl config oms -enable_bip' command
Stopping BI Publisher Server...
BI Publisher Server Already Stopped
BI Publisher is disabled, to enable BI Publisher on this host, use the 'emctl config oms -enable_bip' command
AdminServer Successfully Stopped
BI Publisher Server is Down
BI Publisher is disabled, to enable BI Publisher on this host, use the 'emctl config oms -enable_bip' command
[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl start oms
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.

[oracle@trsen:/u01/app/em13cR2/middle/bin]$./emctl start oms
Oracle Enterprise Manager Cloud Control 13c Release 2  
Copyright (c) 1996, 2016 Oracle Corporation.  All rights reserved.
Starting Oracle Management Server...
WebTier Successfully Started
Oracle Management Server Successfully Started
Oracle Management Server is Up
JVMD Engine is Up

13C em Internal error detected: java.lang.Throwable:oracle.sysman.gcagent.task.scheduler.DispatchingTaskScheduler:1071

In this paper, the reference my oracle support for 13C enterprise manager

1、The mail content ,as follow：
Host=trsen1
Target type=Agent
Target name=trsen.oracle.com:3872
Categories=Diagnostics
Message=Internal error detected: java.lang.Throwable:oracle.sysman.gcagent.task.scheduler.DispatchingTaskScheduler:1071.
Severity=Critical
Event reported time=Jul 25, 2016 11:04:35 AM CST
Operating System=Linux
Platform=x86_64
Associated Incident Id=64
Associated Incident Status=New
Associated Incident Owner=
Associated Incident Acknowledged By Owner=No
Associated Incident Priority=None
Associated Incident Escalation Level=0
Event Type=Metric Alert
Event name=adrIncidentError:diagnosticIncident
Metric Group=Incident
Metric=Diagnostic Incident
Metric value=diagnosticIncident
Key Value=8
Key Column 1=Incident ID
Rule Name=product rule set,rule 1
Rule Owner=SYSMAN
Update Details:
Internal error detected: java.lang.Throwable:oracle.sysman.gcagent.task.scheduler.DispatchingTaskScheduler:1071.

2、view trc file informations on agent instance directory ,as follows:
[oracle@trsen1:/u01/app/oracle/agent13c/agent_inst/diag/ofm/emagent/emagent/incident/incdir_8]$more readme.txt
Incident Id: 8
Incident Source: SYSTEM
Create Time: Mon Jul 25 11:04:35 CST 2016
Problem Key: java.lang.Throwable:oracle.sysman.gcagent.task.scheduler.DispatchingTaskScheduler:1071
ECID: 0000LOVkglD7q2mLsqh8iX1NY4_^00000U
Thread Id: 28
Error Message Id: OFM-99999

Context Values
————–
threadName : GCThread-4
Stack Trace
———–
java.lang.Throwable: Duplicate Scheduled Tasks
at oracle.sysman.gcagent.tmmain.diag.DiagManager.createIncident(DiagManager.java:770)
at oracle.sysman.gcagent.task.scheduler.DispatchingTaskScheduler.checkForDuplicateScheduledTasks(DispatchingTaskScheduler.java:1071)
at oracle.sysman.gcagent.tmmain.lifecycle.TMComponentSvc$SystemMonitoring$CheckForDuplicateScheduledTasksRunnable.run(TMComponentSvc.java:1998)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:304)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:178)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at oracle.sysman.gcagent.util.system.GCAThread$RunnableWrapper.run(GCAThread.java:198)
at java.lang.Thread.run(Thread.java:745)

Diagnostic Dumps

impact:
1、you can receive a large number mail
2、fill the directory where agent instance is located

according to oracle support document information

solution:
1、Take the backup of ../<AGENT_INST>/sysman/config/emd.properties file
2.、Set the following property in emd.properties file:
disableDuplicateTaskCheck= true
3.、Apply the following Bundle Patch:
Patch 23208577: EM-AGENT Bundle Patch 13.1.0.0.160531

The 23208577 patch solution bug ,as follow:
Interim patches (2) :

Patch 23208577 : applied on Mon Jul 25 14:27:07 CST 2016
Unique Patch ID: 20264585
Created on 2 Jun 2016, 18:18:39 hrs PST8PDT
Bugs fixed:
22918272, 21779343, 22616051, 22988508, 23208577, 22384903, 22046370
22304248, 23030165, 22823268, 22720511, 22568679, 22542388, 23507445
22448575, 22293781, 22892276, 22565184, 22684160, 21755932, 22928984