Oracle Enterprise Manager (OEM) Grid Control is monitoring software for Oracle Database, Fusion MiddleWare (FMW including OAS & SOA Suite), Oracle E-Business Suite, Siebel, SAP ….

This post covers overview of various components in OEM Grid Control

Oracle Enterprise Manager (OEM) / Grid Control Component

1. Oracle Management Agent: is software that sits on all nodes(machines) which you would like to monitor. Configuration file for Management Agent is $OH/ <hostname>_<sid>/ sysman/ config/ emd.properties. Agent uploads managed data (from server its monitoring) to Management Service via HTTP Server (URL of management Service HTTP Server is defined by REPOSITORY_URL parameter in emd.properties)
     Management Agent software also includes inbuilt HTTP Listener (different from standalone HTTP Server) to accept messages(data) from Management Service and this URL is defined by parameter EMD_URL in emd.properties.

Management Agent Log & Trace files are in $AGENT_HOME (or $OH/ <hostname>_<sid>) / sysman/ emagent.log, emagent.trcemagentfetchlet.log, emagentfetchlet.trc , emagent.nohup

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2. Oracle Management Service : Management Service upload data (from Management Agent via HTTP Server) to Management Repository (sysman schema in oracle database) using JDBC. Configuration file for Management Service is $OH/<hostname>_<sid>/ sysman/ config/ emoms.properties.
               Repository connection details are defined by parameter emdRepSID, emdRepServer, emdRepConnectDescriptor and emdRepUser in emoms.properties
  Management Service also monitors Management Agent (to check its up and running), submit enterprise manager jobs and other functions using EMD_URL (Management Agent runs inbuilt HTTP listener) defined in emoms.properties

Management Service Log & Tracefiles are in $AS_HOME (or $OH/ <hostname>_<sid>)  / sysman/ emoms.log, emoms.trc
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3. Oracle Management Repository : is Database Schema (sysman) to store Enterprise Manager Data. Management Service connects to Management Repository using JDBC

4. Oracle Enterprise Manager (OEM) Grid Control Console: is browser based tool to monitor and manage targets.  Administrator uses console (URL on browser using webcache post of Grid Control Server) which connects to Webcache Port of OEM Grid Console.  
       Webcache in turn forward request to HTTP server of OEM Grid Middle Tier. HTTP Server retrieve data from Management Repository via Management Service.

5. HTTP Server: recieve requests from webcache, pulls data from Repository via Management Serviceand return response back to Webcache. HTTP Server also receive data from Management Agents, forward it to Management Service to store them in Management Repository.

6. Webcache : acts as web accelerator; forward request from Users (console) to HTTP Server and response back from HTTP server to Users (Console)

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Communication between Management Agent & Service

Management Agent connect to Management Service via HTTP Server of Grid Control Middleware where as Management Service connect directly (using HTTP protocol) to Management Agent (Agent software include inbuilt http server)
 
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References