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Introduction to the concept of CDB and PDB

CDB and PDB are new features introduced by Oracle 12C. In the multi-rent user environment (Multitenant Environment) introduced by ORACLE 12C databases, one database container (CDB) is allowed to host multiple pluggable databases (PDB). The full name of CDB is Container Database, the Chinese translation is database container, and the full name of PDB is Pluggable Database. You can plug and unplug the database. Before ORACLE 12C, the instance and database had an one-to-one or many-to-one relationship (RAC): that is, an instance could only be associated with one database, and the database could be loaded by multiple instances. It is impossible for an instance to have an one-to-many relationship with a database. When entering ORACLE 12C, the instance can have an one-to-many relationship with the database. Here is a diagram of the relationship between CDB and PDB:

A CDB container database usually contains CDB$ROOT and PDB$SEED components:

A. CDB$ROOT stores the metadata provided by ORACLE and Common User,Common User refers to the users who exist in each container. Check out:

Show con_name

B.PDB$SEED is the template for creating a PDB database. There can be only one Seed in a CDB. Check out:

Show pdbs

C.PDB pluggable database. There can be one or more PDB in CDB. Check out:

Show pdbs

Create a CDB container database

When creating a database, dbca can choose whether to create a container database or a traditional database, as shown in the following figure: create CDB:

Create a pdb:

a. The command create pluggable database creates:

Create pluggable database app1 admin user pdba identified by pdba123

Specify the path to create the pdb:

Mkdir-p / u01/app/oracle/oradata/prod/data

Create pluggable database app1 admin user pdba identified by pdba123 FILE_NAME_CONVERT= ('/ u01qapax oraclecosoradata plaza prodactyoradataUniplicactyoradataplicacleoradata')

B.dbca creates a pdb:

Confirm:

Start pdb:

Alter pluggable database APP1 open

c. Clone the pdb database:

Alter system set db_create_file_dest='/u01/app/oracle/oradata/prod/'

Create pluggable database app3 from app2

Delete pdb

Close the corresponding pdb first, and then delete the pdb:

Alter pluggable database app3 close immediate

Drop pluggable database app3 including datafiles

Just delete the library, not the file:

Drop pluggable database app3 keep datafiles

Alter pluggable database app3 unplug into'/ home/oracle/app3.xml'

Drop pluggable database app3 keep datafiles

Show pdbs

Create pluggable database app5 using'/ home/oracle/app3.xml' nocopy

Switch container

Switch to app1 pdb:

Alter session set container=app1

Switch to the CDB container

Alter session set container=CDB$ROOT

See which container you currently belong to:

Show con_name

Select sys_context ('USERENV','CON_NAME') from dual

Start and shut down pdb

a. Specify pdb to shut down and start:

Alter pluggable database app1 open

Startup pluggable database app1

Start to read-only mode. The newly created pdb must be started once before it can be set to read only, otherwise report

ERROR at line 1:

ORA-65085: cannot open pluggable database in read-only mode:

You can confirm it from the dba_pdbs view. For the pdb of NEW, you need to open:

SQL > col pdb_name for A10

SQL > select pdb_name,status from dba_pdbs

PDB_NAME STATUS

--

APP1 NORMAL

PDB$SEED NORMAL

APP2 NORMAL

APP3 NORMAL

APP4 NEW

Create a new app3 database, and then boot to read only:

Create pluggable database app3 from app2

Alter pluggable database app3 open read only

Alter pluggable database app3 open read only

Show pdbs

Alter pluggable database app1 close immediate

B. Switch to the corresponding pdb to shut down and start:

Alter session set container= app1

Startup

Alter session set container= app1

Shutdown immediate

C. Concentrate on pdb:

Open all pdb:

Alter pluggable database all open

Close all pdb:

Alter pluggable database all close immediate

Pdb automatically starts:

Oracle 12.1 and oracle12.2 versions. By default, PDB does not start with CDB startup. Oracle 12.1 can only be implemented through triggers:

CREATE TRIGGER open_all_pdbs

AFTER STARTUP ON DATABASE

BEGIN

EXECUTE IMMEDIATE 'ALTER PLUGGABLE DATABASE ALL OPEN'

END

/

Delete trigger:

Drop trigger open_all_pdbs

After oracle12.2, you can use save state to save the current state of the pdb database.

Show pdbs

Alter pluggable database app1 save state

Startup force

Show pdbs

View state status:

Col con_name for a10

Select con_name, state from dba_pdb_saved_states

Delete discard state status:

Alter pluggable database app1 discard state

View pdb information

View all pdb:

Show pdbs

Col name for a20

Select con_id,dbid,name,open_mode from v$pdbs

Select name,cause, type,message,status from pdb_plug_in_violations

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