作业提交失败 大家帮帮忙

昨天对EM进行了重建，今天打开一切都正常，但对数据库进行调度备份；发生了以下错误：
2008-12-11 08:42:21,156 [MetricCollector:HOMETAB_THREAD600:60] ERROR rt.DbMetricCollectorTarget _getAllData.328 - oracle.sysman.emSDK.emd.comm.CommException: Received unexpected response text : 
<html><head><title>EMDAEMON</title></head><body text="#000000" bgcolor="#FFFFC0"><H1>EMDAEMON</H1><H2> HTTP/1.1 404 , Not Found<br></h2></body></html>oracle.sysman.emSDK.emd.comm.CommException: Received unexpected response text : 
<html><head><title>EMDAEMON</title></head><body text="#000000" bgcolor="#FFFFC0"><H1>EMDAEMON</H1><H2> HTTP/1.1 404 , Not Found<br></h2></body></html>        at oracle.sysman.emSDK.emd.comm.EMDClient.getResponseForRequest_(EMDClient.java:1402)
        at oracle.sysman.emSDK.emd.comm.EMDClient.getResponseForRequest(EMDClient.java:1196)
        at oracle.sysman.emSDK.emd.comm.EMDClient.getMetrics(EMDClient.java:637)
        at oracle.sysman.emo.perf.metric.rt.DbHomeTab._getAllData(DbHomeTab.java:324)
        at oracle.sysman.emo.perf.metric.rt.DbHomeTab.getData(DbHomeTab.java:139)
        at oracle.sysman.emo.perf.metric.eng.MetricCached.collectCachedData(MetricCached.java:402)
        at oracle.sysman.emo.perf.metric.eng.MetricCollectorThread._collectCachedData(MetricCollectorThread.java:596)
        at oracle.sysman.emo.perf.metric.eng.MetricCollectorThread.run(MetricCollectorThread.java:320)
        at java.lang.Thread.run(Thread.java:534)
2008-12-11 08:42:41,203 [MetadataLoad http://noah-pc:3938/emd/main:A0000000001.xml] ERROR eml.XMLLoader FileAsError.733 - Failed to load A0000000001.xml because of errors; moving to errors directory
2008-12-11 08:48:14,843 [EMUI_08_48_14_/console/database/rec/backup] ERROR em.jobs submitJob.1245 - DBJobObject submitJob Exception: java.sql.SQLException: ORA-20900: Could not find credential set DBHostCreds for target type oracle_database
ORA-06512: 在 "SYSMAN.MGMT_CREDENTIAL", line 688
ORA-06512: 在 "SYSMAN.MGMT_CREDENTIAL", line 1351
ORA-06512: 在 "SYSMAN.MGMT_JOBS", line 285
ORA-06512: 在 "SYSMAN.MGMT_JOBS", line 78
ORA-06512: 在 line 1