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Don Burleson Blog 







Multiple Schema Copies on an Oracle Server tips  

Expert Oracle Database Tips by Donald BurlesonUpdated November 24, 2015

Question:  :  We upgrading an Oracle installation. There are multiple schema copies installed on the same server with each schema copy associated with a different customer. We are planning to set up multiple virtual machines with one database per virtual machine.

Is setting up multiple schema copies on one machine using multiple virtual machines a good idea?  Are there any security implications?

Answer:  Other than for running different operating systems on the same server, I do not recommend the use of  virtual machines or VMware.  Even as far back as the 1980's, a mainframe could support a dozen databases, all running a single copy of the database executables. There is no security or other benefit as a result of copying the $ORACLE_HOME/bin.

Overall, it is best to use soft links and one copy of the database, listener.ora, /etc and tnsnames.

A Reader Asks:

" ... consultant suggested that they could install the database once and then just make copies, which would all have the same instance name. We are told that the TNS names can be configured so clients are directed to the right database. I never heard of this and it just seems wrong but I cannot find a reason to advise against this."

The Expert Responds:

 If you are talking about cloning the database, then yes, you can have duplicate ORACLE_SID's on one server, but it is a naive approach.  I wonder about the qualifications of your "expert."

Did your consultant mention VPD as a solution to your multiple schema problem?

 Why maintain multiple copies of an identical schema? If the databases are identical, you want to use Virtual Private Database (VPD) instead.  VPD is made just for having multiple user types sharing a common database.

 It appears that your "expert" does not know about VPD.

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