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.
