Oracle Multitenant Application Containers – Part IX (Move application container across CDBs)

Introduction

In my previous article, I discussed the use of proxy PDBs with application containers to load balance an application across CDBs by relocating application PDB‘s). In this article, I will discuss the moving of an application container to another CDB by unplugging and plugging. It is useful when you need to move the production application container to another CDB.

In order to move the application container to a different CDB, the application container can be unplugged from the source CDB and plugged into the destination CDB. Unplugging an application container involves the unplugging of files for each constituent container (the application root, the application seed, and the application PDBs). An unplug operation can be performed using

• An XML metadata file (.xml extension) that describes the PDB and includes the full paths to the locations of the datafiles associated with the PDB.  In order to plug the PDB into another CDB, the ".xml" file and all the relevant database files must be copied or moved individually over to the destination server.
• A PDB archive file (.pdb extension), introduced in Oracle 12.2.0.1, which is a compressed file that contains
  • The XML file that describes the PDB and contains names of the datafiles associated with the PDB
  • All the datafiles associated with the PDB.

In this case, the transfer of the files between servers is simplified. Only the PDB archive file needs to be copied or moved to the destination server since both the XML metadata file and the PDB datafiles required by the plugging operation are already a part of the archive file.

In this article, I will demonstrate moving an application container to another CDB by unplugging and plugging using archive files. 

Current scenario

The current configuration is shown below in in Fig. 1. We have an Oracle database 12.2.0.1 CDB called orclcdb as shown. Within this CDB, besides the CDB Seed PDB pdb$seed, we have an application container with the application root sales_app_root  for the sales application (sales_app). The application container sales_app_root houses one application PDB app_pdb1 which supports the sales_app application. We also have another 12.2.0.1 CDB called rmtcdb having only one PDB, namely, CDB Seed PDB pdb$seed.

Fig. 1

I will demonstrate moving application container sales_app_root from CDB orclcdb to CDB rmtcdb so that the configuration becomes as shown below in Fig. 2.

Fig. 2

Demonstration

• Connect to CDB orclcdb and note that there is one application container sales_app_root in this CDB.

SQL> conn sys/oracle@orclcdb as sysdba
     set sqlprompt ORCLCDB$ROOT>
     sho con_name
 
CON_NAME
------------------------------
CDB$ROOT
 
 
CDB$ROOT>SELECT con_id, name, open_mode, application_root app_root,
           application_pdb app_pdb, application_seed app_seed
        from v$containers
        where application_root = 'YES' and application_PDb = 'NO' ;
 
   CON_ID NAME       OPEN_MODE APP_ROOT APP_PDB      APP_SEED
---------- --------------- ---------- -------- -------- --------
      3 SALES_APP_ROOT READ WRITE YES     NO NO 

• Connect to application root sales_app_root and note that there is one application seed (sales_app_root$seed) and one application PDB (app_pdb1) associated with it. Also, besides an implicit application, another application sales_app is currently installed in this container. Both the application seed and the application PDB app_pdb1 are synced with sales_app version 1.0.

CDB$ROOT> conn sys/oracle@host01:1522/sales_app_root as sysdba
     set sqlprompt SALES_APP_ROOT>
 
SALES_APP_ROOT>sho con_name
 
SALES_APP_ROOT>@get_app_containers
 
   CON_ID NAME                 OPEN_MODE   APP_ROOT APP_PDB APP_SEED
--------- -------------------- ----------  -------- -------- --------
     3   SALES_APP_ROOT        READ WRITE  YES       NO      NO
     4   SALES_APP_ROOT$SEED   READ WRITE  NO        YES     YES
     5   APP_PDB1              READ WRITE  NO        YES     NO
 
SALES_APP_ROOT>@get_app_status
 
 
APP_NAME                               APP_VERSION APP_ID  APP_STATUS  IMPLICIT
-------------------------------------- ------------ ----- ------------ ------
APP$6020BA8D64AC386FE05364C909C02795   1.0            2    NORMAL       Y
SALES_APP                              1.0            3    NORMAL       N
 
SALES_APP_ROOT>@get_sales_app_pdb_status
 
NAME                 APP_NAME             APP_VERSION APP_STATUS
-------------------- -------------------- ----------- ------------
SALES_APP_ROOT$SEED  SALES_APP            1.0         NORMAL
APP_PDB1             SALES_APP            1.0         NORMAL
 

• There is one common application object associated with the application sales_app, namely the metadata linked table customers owned by sales_app_user.

SALES_APP_ROOT>@get_sales_app_objects
 
APP_NAME    OWNER           OBJECT_NAME     OBJECT_TYPE     SHARING          APPLICATION
---------- ---------------- --------------- --------------- ---------------- ------------
SALES_APP   SALES_APP_USER  CUSTOMERS       TABLE           METADATA LINK     Y
 
SALES_APP_ROOT>desc sales_app_user.customers
 
Name                   Null?       Type
----------------------- --------    ----------------
CUST_ID                NOT NULL   NUMBER
CUST_NAME                        VARCHAR2(30)
CUST_ADD                         VARCHAR2(30)
CUST_ZIP                         NUMBER

• Connect to CDB rmtcdb and note that there is only one PDB, namely, the CDB seed PDB PDB$seed, in this CDB.

SQL> conn sys/oracle@rmtcdb as sysdba
     set sqlprompt RMTCDB$ROOT>
 
RMTCDB$ROOT>sho pdbs
 
  CON_ID    CON_NAME             OPEN MODE   RESTRICTED
---------- --------------------- ---------- ----------
      2     PDB$SEED             READ ONLY   NO
 

Now we will unplug the application container sales_app_root from the CDB orclcdb using archive files and plug it into CDB rmtcdb so as to create a new application container sales_app_root in CDB rmtcdb.

• Unplug the application container sales_app_root from CDB orclcdb using archive files for each container (the application root sales_app_root, the application seed sales_app_root$seed, and the application PDB app_pdb1). Note that we need to proceed in the following order to unplug an application container:

1. The application PDBs dependent on the application root
2. The application seed, if it exists
3. The application root.

ORCLCDB$ROOT>ALTER PLUGGABLE DATABASE sales_app_root CLOSE;
 
             SHOW pdbs
 
  CON_ID   CON_NAME               OPEN MODE RESTRICTED
---------- ----------------------- ---------- ----------
    2      PDB$SEE                 READ ONLY  NO
    3      SALES_APP_ROOT          MOUNTED
    4      SALES_APP_ROOT$SEED     MOUNTED
    5      APP_PDB1                MOUNTED
 
ORCLCDB$ROOT>ALTER PLUGGABLE DATABASE app_pdb1
               UNPLUG INTO '/tmp/app_pdb1.pdb';
 
           ALTER PLUGGABLE DATABASE sales_app_root$SEED
               UNPLUG INTO '/tmp/sales_app_root_seed.pdb';
 
          ALTER PLUGGABLE DATABASE sales_app_root
                UNPLUG INTO '/tmp/sales_app_root.pdb';

As a result of the unplug operation, one compressed archive file having a .pdb extension has been created for each PDB. Since each archive file contains the manifest as well as all the data files of the respective PDB, even if we drop the unplugged PDBs we will still be able to plug them into the destination CDB.

ORCLCDB$ROOT>DROP PLUGGABLE DATABASE app_pdb1 INCLUDING DATAFILES;
 
            DROP PLUGGABLE DATABASE sales_app_root$SEED INCLUDING DATAFILES;
     
            DROP PLUGGABLE DATABASE sales_app_root INCLUDING DATAFILES;
  
            sho pdbs
 
  CON_ID   CON_NAME                 OPEN MODE RESTRICTED
---------- ------------------------ ---------- ----------
      2    PDB$SEED                 READ ONLY   NO

• Create folders on the target server to hold datafiles of the application PDBs to be plugged in.

RMTCDB$ROOT>ho mkdir -p /u02/app/oracle/oradata/rmtcdb/sales_app_root/app_pdb1
 
           ho mkdir -p /u02/app/oracle/oradata/rmtcdb/sales_app_root/sales_app_root_seed

• Plug the sales_app_root application container into CDB rmtcdb. Note that we need to proceed in the following order to plug an application container:

1. The application root.
2. The application seed, if it exists
3. The application PDBs

-- Plug in application root sales_app_root
RMTCDB$ROOT>ALTER SESSION SET
         db_create_file_dest='/u02/app/oracle/oradata/rmtcdb/sales_app_root/';    
 
         CREATE PLUGGABLE DATABASE sales_app_root AS APPLICATION CONTAINER
         AS CLONE USING '/tmp/sales_app_root.pdb';
 
Pluggable database created.
 
RMTCDB$ROOT>@get_app_containers
 
 CON_ID  NAME                OPEN_MODE   APP_ROOT APP_PDB  APP_SEED
-------- ------------------ ------------ -------- -------- --------
  1      CDB$ROOT            READ WRITE  NO        NO           NO
  2      PDB$SEED            READ ONLY   NO        NO           NO
  3      SALES_APP_ROOT      MOUNTED     YES       NO           NO
 
RMTCDB$ROOT>ALTER PLUGGABLE DATABASE sales_app_root OPEN;
 
-- Plug in application seed sales_app_root$seed
RMTCDB$ROOT>CONNECT sys/oracle@host01:1522/sales_app_root AS SYSDBA
           sho parameter db_name
 
NAME                      TYPE       VALUE
------------------------ ---------- -----------------------------
db_name                   string     rmtcdb
 
RMTCDB$ROOT>sho con_name
 
CON_NAME
------------------------------
SALES_APP_ROOT
 
RMTCDB$ROOT>set sqlprompt SALES_APP_ROOT>
 
SALES_APP_ROOT>ALTER SESSION SET
db_create_file_dest='/u02/app/oracle/oradata/rmtcdb/sales_app_root/sales_app_root_seed';
 
SALES_APP_ROOT>CREATE PLUGGABLE DATABASE AS SEED
              AS CLONE USING '/tmp/sales_app_root_seed.pdb';
 
               sho pdbs
 
  CON_ID  CON_NAME                   OPEN MODE   RESTRICTED
--------- ------------------------- ------------ ----------
  3        SALES_APP_ROOT            READ WRITE   NO
  5        SALES_APP_ROOT$SEED       MOUNTED
 
             ALTER PLUGGABLE DATABASE sales_app_root$seed OPEN;
 
-- Plug in application PDB app_pdb1
SALES_APP_ROOT>ALTER SESSION SET
db_create_file_dest='/u02/app/oracle/oradata/rmtcdb/sales_app_root/app_pdb1';
 
               CREATE PLUGGABLE DATABASE app_pdb1
             AS CLONE USING '/tmp/app_pdb1.pdb';
 
               sho pdbs
 
   CON_ID CON_NAME               OPEN MODE   RESTRICTED
---------- --------------------- ----------- ----------
      3 SALES_APP_ROOT           READ WRITE  NO
      4 APP_PDB1                 MOUNTED
      5 SALES_APP_ROOT$SEED      READ WRITE  NO
 
 
SALES_APP_ROOT>ALTER PLUGGABLE DATABASE app_pdb1 OPEN;
 
SALES_APP_ROOT>@get_app_containers
 
 CON_ID   NAME                 OPEN_MODE   APP_ROOT APP_PDB APP_SEED
--------- -------------------- ----------- -------- -------- --------
  3       SALES_APP_ROOT       READ WRITE  YES       NO      NO
  4       APP_PDB1             READ WRITE  NO        YES     NO
  5       SALES_APP_ROOT$SEED  READ WRITE  NO        YES     YES

• Verify that the common application table sales_app_user.customers is accessible from application PDB app_pdb1.

APP_PDB1>desc sales_app_user.customers
Name                            Null?     Type
------------------------------ ---------- ----------------------------
CUST_ID                         NOT NULL  NUMBER
CUST_NAME                                 VARCHAR2(30)
CUST_ADD                                  VARCHAR2(30)
CUST_ZIP                                  NUMBER

Thus, we have been able to move the application container sales_app_root from CDB orclcdb to CDB rmtcdb successfully.

Summary

• An application container can be moved to a different CDB by unplugging it from the source CDB and plugging it into the destination CDB.
• The unplug operation can be performed using
  • An XML metadata file (.xml extension) that describes the PDB
  • A PDB archive file (.xml extension), which is a compressed file that contains
    • The XML file that describes the PDB
    • All the datafiles associated with the PDB.
    • While plugging in using an archive file, only the PDB archive file needs to be copied or moved to the destination server.

References:

• https://oracle-base.com/articles/12c/multitenant-pdb-archive-files-for-unplug-and-plugin-12cr2
• https://docs.oracle.com/database/122/ADMIN/creating-and-removing-pdbs-with-sql-plus.htm#ADMIN13553
• https://docs.oracle.com/database/122/CNCPT/introduction-to-the-multitenant-architecture.htm#GUID-53820A0C-E88A-40C0-AAE0-01A6371A146B
• https://docs.oracle.com/database/122/ADMIN/creating-and-removing-pdbs-with-sql-plus.htm#ADMIN13658
• https://docs.oracle.com/database/122/ADMIN/creating-removing-application-containers-seeds-with-sql-plus.htm#ADMIN-GUID-3A704871-D12B-49E1-98A9-61B6B1DCB187

Scripts use in the article:

get_app_containers.sql
-- Find out the containers in an application root when executed from application root
SELECT con_id, name, open_mode, application_root app_root,
            application_pdb app_pdb, application_seed app_seed
from v$containers 
order by con_id; 
 
get_app_status.sql

-- Find out the status of various applications in an application container when executed from an application root

select app_name, app_version, app_id, app_status, app_implicit implicit from dba_applications;

get_sales_app_pdb_status

-- Find out various versions of application SALES_APP and synchronization status of various application PDBs with it. Execute from application root.

   SELECT c.name,
          aps.app_name,
          aps.app_version,
          aps.app_status
   FROM   dba_app_pdb_status aps
          JOIN v$containers c ON c.con_uid = aps.con_uid
   WHERE aps.app_name = 'SALES_APP';
 
get_sales_app_objects

-- Find out objects belonging to sales_app application.

     select app.app_name, obj.owner, obj.object_name, obj.object_type,
               obj.sharing, obj.application
   from dba_objects obj, dba_applications app
   where obj.owner in
         (select username from dba_users
           where oracle_maintained = 'N')
         and obj.application = 'Y'
and obj.created_appid = app.app_id;