My Oracle Support Banner

Oracle Multitenant: Frequently Asked Questions (Doc ID 1511619.1)

Last updated on JULY 22, 2022

Applies to:

Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Gen 1 Exadata Cloud at Customer (Oracle Exadata Database Cloud Machine) - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Backup Service - Version N/A and later
Information in this document applies to any platform.


This document addresses the frequently asked questions related to Oracle Multitenant achitecture which includes container database (CDB) and pluggable database (PDB).

Questions and Answers

To view full details, sign in with your My Oracle Support account.

Don't have a My Oracle Support account? Click to get started!

In this Document
Questions and Answers
 General CDB / PDB Concept in Multitenant Architecture
 What is a pluggable database (PDB) in Multitenant Architecture?
 Why would I consider using the Multitenant option ?
 What other benefits will I get from Multitenant option ?
 How easy to migrate an existing pre 12.1 database to a Multitenant database ?
 Which Oracle Database features are currently not supported in a Multitenant architecture ?
 Does each non-CDB need its own CDB if I do not have a license for Multitenant?
 Can multiple CDBs run on the same server?
 Can multiple CDBs run out of the same ORACLE_HOME installation?
 Basic Multitenant CDB / PDB Operations
 How do I know if my database is Multitenant or not ?
 What Pluggable databases do we have in this container database ?
 How do I connect to a Pluggable Database , say, PDB6 ?
 How do I switch to main container Database ?
 How do I determine which PDB or CDB I am currently connected to ?
 How do I start up a Pluggable database ?
 How do I shutdown / close a Pluggable database ?
 How do I shut down / Startup the Container Database ?
 Which parameters are modifiable at PDB level ?
 What common users do I have in my cdb ?
 How do I create a common user ?
 How do I create a local user ?
 How do I plug/unplug multiple environments on Oracle Database which apply to different PSU's ?
 Multitenant  Architecture
 What is the difference between Container ID Zero and One ?
 Are there any background processes ex, PMON, SMON etc associated with PDBs ?
 Are there separate control file required for each PDB ?
 Are there separate Redo log file required for each PDB ?
 Can I monitor SGA usage on a PDB by PDB basis?
 Can I monitor PGA usage on a PDB by PDB basis?
 Do I need separate UNDO tablespaces for  for each of my PDB ?
 Do I need separate SYSTEM tablespaces for each of my PDB ?
 Do I need separate SYSAUX  tablespaces for  for each of my PDB ?
 Do I need Temporary tablespaces for  for each of my PDB ?
 Can I specify a separate default tablespace for the root and for each PDB ?
 Are all physical datafiles separate for root and PDB?
 Does Pluggable database support separate database characterset ? 
 How do I configure Net Files in a Pluggable database environment ? 
 How do I establish a bequeath connection to a PDB ?
 Advance CDB / PDB Operations
 How can I install and setup Pluggable Database ?
 What Operations act on PDBs as entities ?
 How can I create a pluggable database ?
 How to drop a PDB irrevocably ?
 How to clone a PDB from an existing PDB ?
 How to unplug a PDB ?
 Scalability & RAC
 How  to add or modify a user-managed service ?
 How can I view which service is attached to my Pluggable database ? 
 Where can I find Alert log for my pluggable Database ?
 Where can I find trace files related for my pluggable Database ?
 If a user-defined, common user creates schema objects in a PDB, and if later that PDB is unplugged
and plugged into a different CDB in which that common user does not exist,
then what happens to the schema objects?
By which user will they be owned?  
Will other users within the PDB, which had been granted privileges on those schema objects, still retain those privileges?
 Is the multitenant option available in Standard Edition?
 Can a transaction span across PDBS ?
 What data can be seen in CDB_ and V$ views from each container?
 May the database timezone be set on a per-PDB basis?
 May NLS currency settings (NLS_CURRENCY et al) be set on a per-PDB  basis?
 How to monitor the undo usage of each container /database in CDB/PDB ?
 What is the difference between schema-based consolidation and the multitenant architecture?
 <Internal_Only>Enhancement Request : 13734561</Internal_Only>

My Oracle Support provides customers with access to over a million knowledge articles and a vibrant support community of peers and Oracle experts.