Pluggable Databases - Expert Consolidation in Oracle Database 12c - page 223

Chapter 7

Pluggable Databases

Pluggable databases, affectionately called PDBs for the remainder of this chapter, are a major new concept in the
Oracle database and the outstanding new feature to be aware of in Oracle 12.1. From the author's point of view the
introduction of Pluggable Databases into the Oracle kernel is a true major new feature of a magnitude which we have
not seen for a long time. In fact, the novelty of this new feature is comparable to the introduction of Automatic Storage
Management in 10g Release 1, which radically changed the way we work with Oracle and storage. In comparison,
the release of 11g Releases 1 and 2 were moderate improvements of the existing previous release—with new features
in certain areas—but nowhere near as novel as Pluggable Databases. The following chapter gives you insight into
managing Pluggable Databases in Oracle 12.1, including the new database types available. I hope that by the end of it
you will be as excited as I am.
It is important to note that Oracle 12.1 is backward compatible with 11g Release 2. So if you are tight on budget
or time it is comforting to know that you do not have to embrace the new feature, but then again you would forfeit
many of the benefits of Oracle 12c. Maybe the following sections are enough of a teaser to start experimenting with
Pluggable Databases.
Note that the use of Pluggable Databases requires you to be correctly licensed for the feature.

The consolidated hosting platform before Oracle 12.1
Pluggable databases address many of the problems administrators and designers faced with consolidation projects
using the previous Oracle releases. Most consolidation projects have used a shared-schema approach where individual
suitable applications have been rebased from their current environments, and often into a (RAC) database. The methods
used to perform the rebasing included Transportable Tablespaces, and ingenious use of the export/import Data Pump
utilities. Some users chose to use replication technologies such as Oracle Streams, Golden Gate, or other third-party
products.
The onboarding process for new applications into the hosted environment usually involves some kind of
assistance from the DBA team or the service owner. The amount of support that can be made available to users of
the hosting service depends greatly on funding. You have to be clear about what the goalposts of the hosting service
are: your solution is either fully automated and therefore users get minimal support from the operational DBAs.
On the other extreme, a dedicated onboarding team exists taking the user through all stages of the application
move, including “intensive care” during the first couple of weeks. Ideally there is a dedicated contact person in the
onboarding team answering any questions. In many situations this ideal may be out of reach.
The hosting service using schema-based consolidation as it existed before Oracle 12.1 had to live with a number
of limitations. Some of these restrictions are of a technical nature; others are procedural. The restrictions include:

• No two identical users can co-exist in a pre-12.1 database.

• Namespaces must be separate.

• There should not be any grant to the PUBLIC role.

• Use of global database links is ruled out due to security constraints.