One more reason to keep them separate: Recovery. What if one client needs the database rolled back? If you have one instance, they are all screwed. Sure, you can do something with Tablespace Point in time recovery. But why make it harder than it needs to be? Keep them in separate instances. -----Original Message----- From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Dennis Williams Sent: Wednesday, July 06, 2005 5:50 PM To: dubey.sandeep@xxxxxxxxx Cc: oracle-l@xxxxxxxxxxxxx Subject: Re: VPD vs multiple schems vs multiple instance Sandeep I would advocate separate instances for the following reasons: 1. Easier security. 2. When downtime is required, easier to meet each client's needs. 3. When Oracle needs patched or upgraded, easier to deal with each client. 4. If you decide to move a client to another server, easily done. For example, one client insists an Oracle patch be applied immediately. Another client insists that they can't possibly accept the downtime required. With a single instance, you are forced to choose between clients. With separate instances you can treat clients independently. There are advantages to a single instance from a shared pool perspective. However, in my experience the frustrations outweigh that gain. Dennis Williams -- //www.freelists.org/webpage/oracle-l -- //www.freelists.org/webpage/oracle-l