Grid Control major components：OMA、OMS and OMR

  The Grid Control framework includes：
  
  ● Oracle Management Repository (OMR)
  ● One or more Oracle Management Service (OMS)
  ● One or more Oracle Management Agent (OMA)
  

  GC 不仅可以管理任何主流的 Oracle 产品、而且还能侦测自定义(比如：路由器)的目标

  

  OMAs 收集目标的信息（比如：可用性、配置和性能）、然后把这些信息传递给 OMS 
  一个 OMA 只和一个 OMS 对话、但一个 OMS 能服务多个 OMA
  接着、OMS 把所接收的信息再抄送一份给 OMR 
  一个 OMS 只和一个 OMR 对话、然而一个 OMR 可服务多个 OMS

  

  ㈠ Oracle Management Agent
     
     The OMA is responsible for ：
     ① all active monitoring 
     ② communication between Grid Control and all managed targets.
     
     The OMA:
     
     ● Must be installed on each host server
               
        A single management agent interfaces the OMS with all managed targets on the host server
               
     ● Must be in its own ORACLE_HOME
               
        Management agents are installed in their own ORACLE_HOME、and
        controlled with the emctl utility
               
     ● Communicates with the OMS via HTTP or HTTPS

     

  ㈡ Oracle Management Service
     
     The OMS is responsible for ：
     ① renders the user interface for Grid Control, works with all OMAs
     ② stores persistent data in the OMR             
     
     The OMS:
     
     ● Includes member components:
        Ⅰ Oracle HTTP Server (OHS)
        Ⅱ Oracle Application Server Containers for J2EE (OC4J)
        Ⅲ OracleAS Web Cache
        
     ● Is a J2EE application deployed on Oracle Application Server 10g
     
     ● Connects to the OMR by using JDBC

      

     You can connect to the GC via a Web browser through OHS and OracleAS Web Cache：
     
     ① OracleAS Web Cache is configured to listen for DBA's connections on port 7777
          and pass the connection through to the OHS on port 7778
        
     ② OMAs connect to the application directly throughOHS, bypassing OracleAS Web Cache
          In most installations, OHS listens for OMA traffic on port 4889
        
        
  ㈢ Oracle Management Repository
  
     The OMR is responsible for ：
     ① organizes the data receiving from OMS so it can be retrieved by OMS and displayed on GC
     
     The OMR:
     
     ● Resides in an Oracle database
     ● Includes schema objects belonging to SYSMAN
        
        The OMR is installed in an Oracle database as a group of approximately 4,000 schema objects
        These schema objects contain information about:
        GC administrators, targets, and applications that are managed by GC
        
     ● Can be installed in a preexisting database
        
        The OMR may be installed either in its own private database orin an existing database