The 'Oracle-as-a-service' strategy has already paid for itself, Tan said.
The project broke even in its first year and was cash positive in its second.
Tan said the CBA had enjoyed a "significant reduction in [the cost of] servers, associated licenses and hosting charges". He said the bank only had to increase its database operations team by one to two people despite adding hundreds of new services.
On a per new application basis, the Oracle-as-a-service approach costs 40 to 50 percent of the cost of building a standalone database server for each app, he said.
It has also led to far speedier provision of new services.
Tan said Oracle database is "traditionally hard to provision" at the speed in which users demand new applications. Under the CBA's strategy, Oracle database "can now be delivered on tap," he said.
"A new development environment can be available within hours, not weeks or months.
"It has removed the need for expensive servers and the bespoke implementation time involved with a highly reliable solution."
For any application, he said, the strategy has allowed the bank to remove the line item for building, deploying and integrating databases out of the project business case.
In maintenance terms, Tan said the shared platform means the bank only has to "patch its database once" and can leverage a single implementation of toolsets across many business systems.
The strategy also provides IT a single point of control for database.
Tan's presentation was met with significant interest by other end user customers at OpenWorld. Streams of questions followed, mostly by users concerned as to how they might secure and guarantee the performance of applications running on a shared database environment.
One end-user asked what would happen if one application on the platform went haywire and impacted the performance of others.
Tan replied that the bank employs a dedicated team of operational DBAs to manage the platform.
"We have a gun team that runs the database," Tan said. "If any business app goes rogue, we turn that service off - which is much the same as if a normal [dedicated database] server had a problem."
The bank uses the resource management and session management modules of Oracle database to "constrain the resources made available to a particular workload in terms of I/O," Tan said.
This enables the bank to protect transaction processing applications (such as online banking apps) from the long running queries in decision support workload (such as queries to or reports from the data warehouse).
Tan said the shared service approach also enables smaller applications to get the "same DBA attention" as larger ones.