How Oracle's pluggable databases will work

IDG News Service - Oracle CEO Larry Ellison revealed this week at the OpenWorld conference that the next version of the company's flagship database, Oracle 12c, would feature a radical new architecture called pluggable databases.

Pluggable databases will allow multiple databases to run under one copy, or instance, of the Oracle database software, a feature he called "multitenancy."

Unlike open-source MySQL databases, work on which is largely conducted in public view, Oracle's work on its flagship database is largely conducted behind closed doors. So, the company did not reveal many details about how pluggable databases would work and the software is not due to be released for another year.

However, some basic details emerged in the days after Ellison's announcement Sunday.

Two of Oracle 12c's principal architects -- Oracle distinguished product manager Bryn Llewellyn and Oracle architect Kumar Rajamani -- talked at one conference session about how Oracle 12C differs from the current Oracle 11g database. Oracle Vice President Tom Kyte, who authors the popular Ask Tom Oracle technical blog, also spoke more about how pluggable databases will help users.

In a nutshell, the new design splits today's database into two separate entities, an act Llewellyn called "architectural separation." One portion, often referred to as the Root or the container database, will hold all the functionality and metadata required to run the database itself. The second portion will be the user's database and it will be independent from the container database.

"We separate Oracle's metadata from the tenant's metadata," Llewellyn explained. "The root contains Oracle's metadata, while the pluggable database contains the customer metadata."

Dividing the database operations cleanly from the user's content is a major transformation from traditional database architectures. Oracle 11g, and all its predecessors, could only run one database at a time, Kyte said. If an organization wanted to run multiple databases on a single server, it would need to run multiple instances of Oracle 11g, one for each database.

As the name implies, pluggable databases allow multiple tenant databases to run under one copy of Oracle 12c. In fact, Oracle 12c can run up to 250 user databases, Llewellyn said, adding that 250 is an arbitrary number that Oracle chose, and the architecture could probably support more. The new database is compatible with older Oracle databases, Llewellyn said.

This change in architecture brings a number of benefits that Oracle touted through the week, including improved efficiency, stronger security and easier upgrades.

Today, many organizations are running multiple databases on a single server or they try to build a huge database that supports multiple applications. Both approaches are inefficient, Oracle argued through the week.