Sunday, August 21, 2016

Where Oracle 12c Multitenant can (and should) be improved


Since it was introduced in Oracle Database 12c, the new exciting Oracle Multitenant architecture makes the Oracle DBA's life much easier in terms of administration and management. It allows to manage many Oracle Databases as one and by doing so it solves many consolidation challenges.
In this post, I would like to review 3 items where I believe Oracle can (and should) improve its Multitenant capabiliities:
  • DBCA Installation
  • Flashback Database
  • Memory Resource Management
  • PDB Cloning

DBCA Installation

During an installation of Oracle 12c with a container database (A.K.A multitenant), DBCA doesn't allow deselecting database options and it basically force you to install all the optional database options. See the following screenshot for example:

I think it would be nice if Oracle will allow deselecting database options because the current design has few disadvantages:
  • It makes the installation process much longer
  • It consumes more disk space
  • Installing unneeded database options may raise the chances to hit potential bugs.
I've raised an idea in the Oracle community to allow deselecting database options during Oracle 12c Multitenant installation. See:

Flashback Database

The "Flashback Database" feature is supported only at the CDB-level, and it does not allow a "granular flashback" at the PDB-level. In many cases, the requirement is to rewind one specific application (i.e. PDB), and not the entire CDB. RMAN, for example, allows a PDB point-in-time-recovery, so the same granularity should also be available in the FLASHBACK DATABASE feature. 
I've raised an idea in the Oracle community to allow using the Flashback Database feature at the PDB-level. See:

Memory Resource Management

In Oracle 12c, Oracle Resource Manager has been enhanced to support Multitenant by allowing to limit and prioritize CPU resources among competing PDBs. Currently it is not possible to prioritize memory resources; For example, today we cannot specify which PDBs will have higher priority for SGA areas than other PDBs. The outcome of this is that potentially a low-priority PDB can consume most of the SGA buffers. 
I've raised an idea in the Oracle community to enhance Oracle Resource Manager to be able also to limit and prioritize memory resources among competing PDBs.

Online PDB Cloning
Cloning a PDB is a great feature which allows fast provisioning by creating a copy of a PDB either from another PDB within the same CDB, or from another PDB in a remote CDB. The problem with this feature is that cloning a PDB requires the source PDB to be in OPEN READ ONLY mode which essentially requires a down time as no DML/DDL operations are allowed on PDB when it's in a READ ONLY mode.


Generally speaking, Oracle multitenant is a full-featured product with many advantages. I would definitely recommend every Oracle DBA to upgrade to Oracle 12c Multitenant. Yet, I believe that there are some areas where Oracle can and should improve regarding its Multitenant feature and I hope we will see some Multitenant enhancements in the upcoming Oracle release (12cR2). 


  1. concerning DBCA Installation: the real problem here is the "license" because not all organizations require oracle spatial or label security which Oracle will ask the customer to pay extra money for utilization.

  2. Hi, Its nice and useful. Hope this may useful and helpful.