I had deconfig em with "emca -deconfig all db". Then execute "emca -config all db" to re-config. It reported error to configured central management.
Following it content of log. It seems emca cannot find emtgtctl under /oracle/product/11.2.0/dbhome_1/bin. But the emtgtctl exists at the location it require.
CONFIG: Oracle Enterprise Manager 11g Database Control Release 11.2.0.1.0
Copyright (c) 1996, 2009 Oracle Corporation. All rights reserved.
0 [main] ERROR emSDK.config - Warning: one of following could not be found:/oracle/product/11.2.0/dbhome_1/bin/emtgtctl or /oracle/product/11.2.0/dbhome_1/localhost.localdomain_ccraft/bin/emtgtctl
5 [main] ERROR emSDK.config - oracle.sysman.emSDK.conf.CentralHomeAdditionException: emtgtctl could not be found in the bin directory of either the local home at /oracle/product/11.2.0/dbhome_1 or the central home at /oracle/product/11.2.0/dbhome_1/localhost.localdomain_ccraft
oracle.sysman.emSDK.conf.CentralHomeAdditionException: emtgtctl could not be found in the bin directory of either the local home at /oracle/product/11.2.0/dbhome_1 or the central home at /oracle/product/11.2.0/dbhome_1/localhost.localdomain_ccraft
at oracle.sysman.emSDK.conf.TargetInstaller.addCentralAgentHome(TargetInstaller.java:1931)
at oracle.sysman.emSDK.conf.TargetInstaller.main(TargetInstaller.java:3167)
Apr 7, 2010 6:30:17 PM oracle.sysman.emcp.util.PlatformInterface executeCommand
CONFIG: emtgtctl could not be found in the bin directory of either the local home at /oracle/product/11.2.0/dbhome_1 or the central home at /oracle/product/11.2.0/dbhome_1/localhost.localdomain_ccraft
Apr 7, 2010 6:30:17 PM oracle.sysman.emcp.util.PlatformInterface executeCommand
WARNING: Error executing /oracle/product/11.2.0/dbhome_1/bin/emctl config agent addcentralagent /oracle/product/11.2.0/dbhome_1 /oracle/product/11.2.0/dbhome_1
Apr 7, 2010 6:30:17 PM oracle.sysman.emcp.util.CentralAgentUtil registerWithCentralAgents
CONFIG: Error registering with /oracle/product/11.2.0/dbhome_1
Apr 7, 2010 6:30:17 PM oracle.sysman.emcp.EMAgentConfig performConfiguration
WARNING: Error registering database targets with the central agent(s).
Apr 7, 2010 6:30:17 PM oracle.sysman.emcp.EMConfig perform
SEVERE: Error configuring central management. This target will not be centrally managed
Refer to the log file at /oracle/cfgtoollogs/emca/ccraft/emca_2010_04_07_18_28_15.log for more details.
Apr 7, 2010 6:30:17 PM oracle.sysman.emcp.EMConfig perform
CONFIG: Stack Trace:
oracle.sysman.emcp.exception.EMConfigException: Error configuring central management. This target will not be centrally managed
at oracle.sysman.emcp.EMAgentConfig.performConfiguration(EMAgentConfig.java:1491)
at oracle.sysman.emcp.EMAgentConfig.invoke(EMAgentConfig.java:290)
at oracle.sysman.emcp.EMAgentConfig.invoke(EMAgentConfig.java:268)
at oracle.sysman.emcp.EMConfig.perform(EMConfig.java:259)
at oracle.sysman.emcp.EMConfigAssistant.invokeEMCA(EMConfigAssistant.java:589)
at oracle.sysman.emcp.EMConfigAssistant.performConfiguration(EMConfigAssistant.java:1448)
at oracle.sysman.emcp.EMConfigAssistant.statusMain(EMConfigAssistant.java:573)
at oracle.sysman.emcp.EMConfigAssistant.main(EMConfigAssistant.java:521)
Apr 7, 2010 6:30:17 PM oracle.sysman.emcp.EMConfig restoreOuiLoc
CONFIG: Restoring oracle.installer.oui_loc to /oracle/product/11.2.0/dbhome_1/oui