step by step to identify PDB or CDB

How to identity am i connected PDB or CDB?

In Oracle Database 12c, we can still find this information from V$INSTANCE.  Breath a sigh of relief, for the moment!  What if I connect to a container database and then issue an ALTER SESSION command to move into a different container, i.e. as PDB?  Will I get the name of the PDB that I move into from the V$INSTANCE view or do I need to look somewhere else?  Lets take a look.

Connect to the container database as usual and use the V$INSTANCE view to see where I’m at.

[oracle@r12c ~]$ sqlplus "/as sysdba"

SQL*Plus: Release 12.1.0.2.0 Production on Fri Sep 11 10:52:33 2015

Copyright (c) 1982, 2014, Oracle.  All rights reserved.


Connected to:
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options

SQL> select instance_name, version, status, con_id from v$instance;

INSTANCE_NAME    VERSION           STATUS           CON_ID
---------------- ----------------- ------------ ----------
cdb1             12.1.0.2.0        OPEN                  0

Lets move into a PDB.  I have created the ORCL.

SQL>alter session set container=ORCL;

Session altered.

Did I actually move containers?  How can I tell?  Instead of selecting INSTANCE_NAME from V$INSTANCE; we have two new SHOW commands that will provide us the information we are looking for.  These command are quite simple (SHOW CON_ID & SHOW CON_NAME).

SQL> show con_id;

CON_ID
------------------------------
4
SQL> show con_name

CON_NAME
------------------------------
ORCL

This view provides similar information as V$INSTANCE does; yet is only specific to PDBs.  If we wanted to find out the container_id, name, open_mode and size of the PDB we are currently connected to, we can use this query:


SQL> select con_id, name, open_mode, total_size from v$pdbs;

    CON_ID NAME                           OPEN_MODE  TOTAL_SIZE
---------- ------------------------------ ---------- ----------
         4 ORCL                           READ WRITE 2945187840

SQL>

What is interesting to point out, is that since we used an ALTER SESSION statement to switch to PDB1, the V$PDBS view only lists the PDB we are currently working in.  If we want to get a complete list of PDBs within the container database, we need to go back to the root container database and run the same SQL statement.

SQL> alter session set container=CDB$ROOT;

Session altered.

SQL> show con_name;

CON_NAME
------------------------------
CDB$ROOT
SQL> select con_id, name, open_mode, total_size from v$pdbs;

    CON_ID NAME                           OPEN_MODE  TOTAL_SIZE
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY   838860800
         4 ORCL                           READ WRITE 2945187840

SQL>