[Enterprise Vault Operations Manager start page]
"An error has occurred" - \EnterpriseVault\monitoringweb\ErrorPage.aspx
Health monitoring is not enabled
Enable health monitoring in web.config and try and reproduce the error. The error details will be logged in the logs\log.txt

To confirm the error condition take a Dtrace of the MonitoringMiddleTier exe while recreating the issue.
[Dtrace]
531 15:45:05.153 [4844] (MonitoringMiddleTier) <9484> EV-H {MIDDLETIERDATAMANAGER.EN_US} Exception: Info: Diag: Type:Symantec.EnterpriseVault.OperationsManager.DataAccessLayer.MonitoringAccessDBException ST: at Symantec.EnterpriseVault.OperationsManager.DataAccessLayer.Common.DBHelper.FillFromXmlCommand(DataSet[] dataSets, SqlCommand xmlCommand, ConnectionProvider connProvider)| at Symantec.EnterpriseVault.OperationsManager.DataAccessLayer.Monitoring.MonitoringDataManager.FillConfiguration(MonitoringDataSet dataSet)| at Symantec.EnterpriseVault.OperationsManager.MiddleTierDataAccessLayer.MiddleTierDataManager.GetConfiguration(MonitoringDataSet& monDataSet) Inner:System.Data.SqlClient.SqlException: The EXECUTE permission was denied on the object 'GetSiteConfigXML', database 'EnterpriseVaultMonitoring', schema 'dbo'.| at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection)| at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection)| at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj)| at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)| at System.Data.SqlClient.SqlDataReader.ConsumeMetaData()| at System.Data.SqlClient.SqlDataReader.get_MetaData()| at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString)| at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async)| at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)| at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)| at System.Data.SqlClient.SqlCommand.ExecuteXmlReader()| at Symantec.EnterpriseVault.OperationsManager.DataAccessLayer.Common.DBHelper.FillFromXmlCommand(DataSet[] dataSets, SqlCommand xmlCommand, ConnectionProvider connProvider)
533 15:45:05.168 [4844] (MonitoringMiddleTier) <9484> EV-H {SERVERSINK.EN_US} Exception: Object reference not set to an instance of an object. Info: Diag: Type:System.NullReferenceException ST: at Symantec.EnterpriseVault.OperationsManager.MiddleTierDataAccessLayer.ServerSink.InternalProcessMessage(IMessage response) Inner:None
[Enterprise Vault Operations Manager log (Health Monitoring)]
Provider name: BufferedFileWebEventProvider
Buffering:
Buffering modality:
Event code: 100001
Event message: Symantec.EnterpriseVault.OperationsManager.MiddleTierDataAccessLayer.MonitoringMiddleTierException - Exception caught in MiddleTier(MiddleTierDataManager::GetConfiguration)
Event time: 11/14/2011 1:34:06 PM
Event time (UTC): 11/14/2011 1:34:06 PM
Event ID: e5266b569934464a9883b5d089b3fbd
Event sequence: 6
Event occurrence: 1
Event detail code: 0
Request information:
Request URL: https://EVServer:443/monitoringwebapp/EVMonSummary.aspx
Request path: /monitoringwebapp/EVMonSummary.aspx
User host address: 10.10.10.1
User: EV\EVOM-user
Is authenticated: True
Authentication Type: Negotiate
Thread account name: EV\EVOM-user
Custom event details:
* Application Event Information Start *
Event created at: 14/11/2011 13:34:06
Symantec.EnterpriseVault.OperationsManager.MiddleTierDataAccessLayer.MonitoringMiddleTierException: Exception caught in MiddleTier(MiddleTierDataManager::GetConfiguration)
To enable Health monitoring within EVOM:
1. Edit web.config file in the WebAppMonitoring application in IIS.
2. Replace line
Microsoft information about healthMonitoring Element: msdn.microsoft.com/en-us/library/2fwh2ss9(v=vs.80).aspx
The EVOM account as set in IIS does not have the required permissions to access the configuration settings.
To correct this issue the proper credentials and permissions need to be updated in EVOM.