Application containers:
An application container consists of an application root and one or more
application PDBs. The container stores data for a specific application, which
contains common data and metadata. You can upgrade or patch the
application once in the application root, and then synchronize the application
PDBs with the root.

Reference book:
Oracle Database 12c Release 2 Multitenant by Franck Pachot, Vit Špinka, Anton Els.

Create Application root:

Login to the CDB root as SYSDBA and create an application root named shan_app.

[oracle@multisrv1 ~]$ ps -ef|grep pmon
grid 4986 1 0 22:10 ? 00:00:00 asm_pmon_+ASM
oracle 5086 1 0 22:10 ? 00:00:00 ora_pmon_CDB1
oracle 6241 6216 0 22:39 pts/0 00:00:00 grep pmon
[oracle@multisrv1 ~]$ sqlplus sys/oracle@cdb1 as sysdba

SQL*Plus: Release 12.2.0.1.0 Production on Sun Feb 3 22:39:37 2019

Copyright (c) 1982, 2016, Oracle. All rights reserved.


Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

SQL>

CREATE PLUGGABLE DATABASE shan_app AS APPLICATION CONTAINER
ADMIN USER shan_appadm IDENTIFIED BY oracle;
ALTER PLUGGABLE DATABASE shan_app OPEN;
col name format a10
SELECT CON_ID, NAME, OPEN_MODE
FROM V$PDBS WHERE APPLICATION_ROOT='YES';
CON_ID NAME OPEN_MODE
---------- ---------- ----------
5 SHAN_APP READ ONLY

— save the state of shan_app (otherwise, it will be closed when you reboot):

ALTER PLUGGABLE DATABASE shan_app SAVE STATE;

View the tablespaces and the datafiles created for the application container shan_app.
Obtain the CON_ID value from the query in the previous step.
Observe that the tablespaces SYSTEM, SYSAUX, and UNDOTBS1 are created.

SQL> SELECT FILE_NAME, TABLESPACE_NAME FROM CDB_DATA_FILES WHERE CON_ID=5;

FILE_NAME
--------------------------------------------------------------------------------
TABLESPACE_NAME
------------------------------
+DATA/CDB1/80F305B39D922445E0535800A8C090A6/DATAFILE/system.275.999230255
SYSTEM

+DATA/CDB1/80F305B39D922445E0535800A8C090A6/DATAFILE/sysaux.276.999230255
SYSAUX

+DATA/CDB1/80F305B39D922445E0535800A8C090A6/DATAFILE/undotbs1.274.999230255
UNDOTBS1


Switch the current container to the application root and check which privilege is granted to SHAN_APPADM
Observe that the application root administrator is only granted the role PDB_DBA. This role has three privileges granted to it.
ALTER SESSION SET CONTAINER=SHAN_APP;
-- check the roles granted to the user:
col grantee format a10
col granted_role format a15
SELECT GRANTEE, GRANTED_ROLE, COMMON
FROM DBA_ROLE_PRIVS where GRANTEE ='SHAN_APPADM';
-- check the privileges granted to the role:
col role format a10
col privilege format a30
SELECT ROLE, PRIVILEGE, ADMIN_OPTION, COMMON, INHERITED
FROM ROLE_SYS_PRIVS WHERE ROLE='PDB_DBA';

Configure the tnsnames.ora file to allow connecting to the application root through the listener.

vi tnsnames.ora
SHAN_APP =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = srv1)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = shan_app.localdomain)
)
)

Test the configuration

conn sys/oracle@shan_app as sysdba

Install an application in the application root

Login to the application root as SYSDBA.

conn sys/oracle@shan_app as sysdba

Begin installing the HR_APP application.
Note: When you install a new application in an application root, you always start with this statement.

ALTER PLUGGABLE DATABASE APPLICATION hr_app BEGIN INSTALL '1.0';

Create the application tablespace (HR_TBS) and create the application owner user (HR).
The application owner (HR) should have the privileges enough to control the application objects, like the application tables, indexes, sequences, PL/SQL program units… etc.
The application owner is common user in the application root.

CREATE TABLESPACE hr_tbs;
CREATE USER HR IDENTIFIED BY oracle DEFAULT TABLESPACE HR_TBS QUOTA UNLIMITED ON HR_TBS CONTAINER = ALL;
GRANT CREATE SESSION, CREATE TABLE, CREATE SEQUENCE, CREATE VIEW, CREATE PROCEDURE, CREATE TRIGGER TO HR;

Switch the current schema to the application user.

ALTER SESSION SET CURRENT_SCHEMA=hr;

Run the script file.

@<run the sql for the appication objects creation>.sql

End the application installation, if all the commands in the script successfully run.

ALTER PLUGGABLE DATABASE APPLICATION hr_app END INSTALL '1.0';

Verify that the application has been successfully created.

column app_name format a15
column app_version format a10
column app_status format a15
SELECT APP_NAME, APP_VERSION, APP_STATUS FROM DBA_APPLICATIONS WHERE APP_IMPLICIT='N';