I'm learning a little bit about Oracle Database. As I understand:

  • In previous versions of Oracle DB (versions <= 11ng), each DB should be installed in a separate server.

    1. Is this statement true? We can't create more than of one database in each instance of Oracle installation? or I'm missing something here.
  • To take care of the problem, oracle updated its architecture and introduced the pluggable databases.

    1. Why not just using the same architecture of other DBMS systems like MySQL whre you can have N number of databases in you single installation of DBMS?

I'm guessing that I'm not fully understanding the first statement as I never had any experiences with Oracle Database.

1 Answer 1


Two things going on here:

First, Oracle defines "database" differently than other "databases" like MySQL. When Oracle talks about a database, they mean the physical instance of the software, data files, and processes that run on on the server. Each database instance may house hundreds or thousands of individual users/schemas, each with their own tables and other objects. It is possible to run multiple database instances on a single server - even using different versions of the software simultaneously. Operating multiple instances/databases - usually but not always of the same version - on a single server is quite common, actually.

Most other database engines equate "database" with a single schema of objects, and often only support one installation of the software on an individual server, though they may house hundreds or thousands of users/schemas.

Second, Oracle's pluggable databases (introduced in Oracle 12c) are a virtualization of the database instance (the running processes, data files, etc.) that allows them to share some common, system-level resources. A container database (CDB) manages those system level resources, and may host many pluggable databases (PDB). A single server may host multiple container databases of different software versions, each with their own pluggable databases. Each pluggable database may contain hundreds or thousands of users/schemas. The pluggable database architecture allows for consolidation of compute and storage resources: a higher density architecture that makes more efficient use of both on-premise and cloud hardware.

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