In development for roughly four years, Oracle Database 12c introduces so many important new capabilities in so many areas -- database consolidation, query optimization, performance tuning, high availability, partitioning, backup and recovery -- that even a lengthy review has to cut corners. Nevertheless, in addition to covering the big-ticket items, I'll give a number of the lesser enhancements their due.
Having worked with the beta for many months, I can tell you that the quality of software is also impressive, starting with a smooth RAC cluster installation. As with any new software release, I did encounter a few minor bugs. Hopefully these have been resolved in the production release that arrived yesterday.
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Pluggable databases
Consolidation is an important business strategy to reduce the costs of infrastructure and operational expenses. In many production database servers, a big portion of CPU cycles go unused. By consolidating many databases into fewer database servers, both the hardware and operational staff can be more effectively utilized.
But database consolidation is easier said than done. Critical issues such as database workload characteristics, the ability to maintain performance service levels, and point-in-time recovery needs of different databases must be considered during consolidation efforts. Ideally, consolidation would not only reduce the need to purchase and allocate less physical CPU, RAM, and I/O (because physical servers are underutilized), but would also reduce actual resource consumption (because multiple instances share some overhead). However, in the past, we've seen that co-locating databases physically in the same server does not reduce overall resource usage.
Oracle's new pluggable database feature reduces the risk of consolidation because the DBA can easily plug or unplug an existing database to or from a container database. There is no need to change any code in the application. When the user connects to a plugged database, the database environment looks exactly as if the user had connected to a traditional database.
Further, pluggable databases do lower resource consumption. Memory and processes are owned by the container database and shared by all pluggable databases, improving resource usage overall. It is also easy to unplug a database and convert the pluggable database to a traditional database if required. In addition, you can back up and recover pluggable databases independently of the container database; you can also perform a point-in-time recovery of a pluggable database. Further, Resource Manager can be used to control resources consumed by a pluggable database.
In short, database consolidation can be done much more effectively with pluggable databases than ever before. Finally, we have a true cloud database.
Optimizer features
Version 12c introduces a few useful Oracle PL SQL Training Optimizer features, and most of these are automatically enabled.
Although Optimizer has matured over the years, it is still not uncommon for Optimizer to choose an inefficient execution plan due to incorrect cardinality estimates, invalid statistics, or even stale statistics. This can have dire results. A SQL statement estimated to run for a few seconds might take hours to execute if the chosen execution plan is not optimal.
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