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Don Burleson Blog 







Performance of multiple schemas in a single instance 

Oracle Database Tips by Donald BurlesonJune 6, 2015

Question:  We have many individual clients using the same software. SaaS model. The current number of clients is around 60, with some very large, and many moderately small in data volumes.

1) Securing client data to protect data privacy and to eliminate the possibility of accidental cross-client access. In some cases we are contractually bound to separate information.

2) Hosting firm charges support per instance, and Oracle licensing costs are through the roof.

We've used VPD in the past, and are moving away from it for performance reasons and ease of individual client maintenance tasks.

My question is, with 11g and Workload Management, can multiple schemas (1 per client), perform?  I have numerous reasons why multiple schemas would be better from a database administration perspective, but I don't want to hurt performance.

Answer:  I liked VPD from a reduced administrative perspective, but if you don't have a problem maintain multiple schemas, then there should be no problem with many separate schemas, all running inside the same instance!  In some cases, separate schemas make it easier to manipulate performance.  For example, with multiple schemas, I can assign one table for one schema owner to the KEEP pool, while excluding other schemas.

I've worked in many shops with "cloned" schemas, no problem,  and I have details in my book "Oracle Tuning: The Definitive Reference":

>> In some cases we are contractually bound to separate information.

Ha!  I've seen that before, and it's largely about ignorance!  Separation of data does not improve security, but I've seen it used as a lame argument against VPD's!



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