Overview

Multitenancy is a new concept in Oracle 12c. The basis of it is that, you can separate the application data from the system data. Up to and including 11g, all the data in the database was residing in the same dimension as the system data or any other data for that matter. Data related to different application, were in the same tablespaces or even managed by the same user. Well, from 12c, all this can go under the table, now you can have many databases PDBs (pluggable databases), inside one big database, the root container. There are even more possibilities like application containers and so on, but we will see that later.

With the multi-tenancy, we have a:

root container - Where the system data resides. Also you can choose if you want the UNDO tablespace in the root to be used for all PDBs, or each PDB to have its own undo, SYSTEM and SYSAUX tablespace, making it completely independent from the root container.

Application Container - Container which consist of 1 or many PDBs which host a specific application. We are able to assign versions and name to such container, furthermore we can initiate installation and upgrade modes.

Using SQL

Firstly, we need to create our container. From 12c, we can create a database to be either as it always has been, a normal database, OR we can create it to allow other databases as well. So it will be a container, let's see how we can do both:

Creation

Actually, the creation of a normal database isn't that hard, you can just type:

Create simple database

Simply that, will create us a normal database, well after that you will have to run the catproc and the catalog scripts, but you get the gist.

Create container DB

To create a container, database we NEED to allow it to have PLUGGABLE databases, as follows:

Create CDB

That will create us a container database called CDB1 and a SEED, after that you will have to run script:

@$ORACLE_HOME/rdbms/admin/catcdb.sql

But other than that, all will be ok. So we have a container, big deal, what then. Well, now we can create PLUGGABLE databases as follows:

Create Pluggable DB (PDB)

As I said before, pluggable databases, are totally separate databases from one another. Imagine it having many databases (PDBs) within one big database (CDB). These PDBs, can have separate user totally individual from each other. So let's see how it is done:

Create PDB

You can use either:

FILE_NAME_CONVERT, or

CREATE_FILE_DEST, or

PDB_FILE_NAME_CONVERT

Either in the session level or on the CREATE statement, up to you, the result will be the same.

Once created, you can list all PDBs in a certain CDB as follows:

List PDBs

Remember, 1 PDB can be in only 1 ROOT$CDB, but 1 CDB can have many PDBs. Furthermore, from 12.2, we have also applicational containers, which are containers within the CDB, but we will speak about them in a second.

Using DBCA

We can use DBCA to create and delete CDB and PDBs as follows:

Examples

Automation

Using the awesome power, vested to me by Vagrant and Bash, I summon the automation of:

Virtual Machine

Oracle 19c database

1 CDB

1 PDB

All that, twice:

Automation

Just make sure, you have the Oracle 19c RPM in folder called: “lpar_binaries” in your Vagrant main folder and the response file below:

Response file

Of course feel free to add / remove or modify any parameter which you wish. Just bare in mind that some are mandatory :)