This is a difficult question for me to answer because I have no information about your environment. Setting up Oracle 10g Grid Control is going to take some time and effort, there is no doubt, especially if you have many servers. There are Intelligent Agents to install and you are somewhat correct about Oracle9i databases. Grid Control will work with Oracle9i databases but if 10g features are not available, they will be greyed out so you cannot take advantage of those features. Oracle 10g Grid Control, however, does have some very nice features that may make the implementation of it worthwhile in your environment.
My suggestion would be to create a small project to evaluate Oracle 10g Grid Control in your environment. Choose a test server to set up Grid Control and choose several test database servers on which to install the Intelligent Agents. Decide which features of Grid Control would be most beneficial to you and then test these features over the course of a few weeks or months. If they behave satisfactorily and Grid Control makes your day-to-day duties more manageable, then you should consider implementing it across your entire environment.
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