Using multiple Oracle homes to apply a patch

How do you use Oracle Enterprise Manager without a database or does this require Opatch from the command line?

In the April 26 "Ask The Oracle Expert" newsletter there was a link to " Five DBA best practices." Number 1 is using multiple Oracle homes to help prevent a problem when patching if the patch causes an issue. I really like the concept but I'm having difficulty with applying the idea to Oracle 10g on Windows since there are services involved that reference paths and using Enterprise Manager to apply the patches. How do you use EM without a database or does this require Opatch from the command line? Thanks!

I, too, found Arup Nanda's tips in "Five DBA best practices" very helpful. The first tip where he discusses creating an entirely new Oracle Home to apply a patch could refer to applying a one-off patch, a CPU or a patch set. I, typically, do not use Enterprise Manager to apply patches so I am unsure of the process involved, but I see no reason why Arup's tip would not apply to both Unix and Windows operating systems. Basically, Arup is suggesting that an entirely new Oracle Home be created the same as the existing Oracle Home. Be sure to install the same components and patches. You would then apply the new patch to the new Oracle Home. During a scheduled outage window, you would shut down the database, point it at the new Oracle Home and your database would be upgraded. If there is a problem, you could shut the database down and point it back to the original Oracle Home.

One word of caution is that, depending on the patch, there may or may not be an additional step of running a database script. If the patch requires that changes be made to the data dictionary, it may not be as easy to back out. As well, if you are applying a patch set (e.g., to you may have to restore your database to revert back to the previous release. The installation documents that accompany the patches or patch sets will clearly advise you of the back out procedure available.

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