Oracle Multitenant Migration

 Oracle Multitenant Migration

Multitenant Support 

What does this mean?

 1. Oracle Database 19c is the last release to support non-CDB architecture

2. Before upgrade to Oracle Database 21c or beyond, you must convert to the mulititenant architecture .

MUTLITENANT MIGRATION

CDB | Components 

CDB$ROOT must be a superset of all PDBs

Recommendation

 1. Install as many components as required 

2. But no more than that 

Number of components have big effect on upgrade duration Components (e.g., JAVAVM) may require patch regular activity

• Always use default of a given version

    • Example 19.0.0

    • Always use three digits only

• Should you change COMPATIBLE after applying a Release Update?

    • Example 19.10

    • Never

Plug In | Compatibility Check 

1. In source, generate manifest file

SQL> exec dbms_pdb.describe('/tmp/DB19.xml');

 2. In CDB, check compatibility

set serveroutput on

BEGIN

IF dbms_pdb.check_plug_compatibility('/tmp/DB19.xml') THEN

dbms_output.put_line('PDB compatible? ==> Yes');

ELSE

dbms_output.put_line('PDB compatible? ==> No');

END IF;

END;

/

3. Always check the details

SQL> select type, message

from PDB_PLUG_IN_VIOLATIONS

where name='DB19' and status<>'RESOLVED';

TYPE         MESSAGE

___________________________________________________________________________________

ERROR '19.9.0.0.0 Release_Update' is installed in the CDB but no release updates are installed in the PDB

ERROR DBRU bundle patch 201020: Not installed in the CDB but installed in the PDB

ERROR PDB's version does not match CDB's version: PDB's version 12.2.0.1.0. CDB's version 19.0.0.0.0.

WARNING CDB parameter compatible mismatch: Previous '12.2.0' Current '19.0.0'

WARNING PDB plugged in is a non-CDB, requires noncdb_to_pdb.sql be run. 

Plug In | Create PDB

1. Restart database in read-only mode

2. Generate manifest file and shut down

3. In CDB, create PDB from manifest file

SQL> shutdown immediate

SQL> startup mount

SQL> alter database open read only;

SQL> exec dbms_pdb.describe('/tmp/DB19.xml');

SQL> shutdown immediate;

SQL> create pluggable database DB19

using '/tmp/DB19.xml' nocopy tempfile reuse;

Convert | Create PDB

1. Open PDB

2. Convert and restart

3. Restart PDB

4. Check plug-in violations

5. Purge

6. Ensure PDB is open READ WRITE and unrestricted

7. Configure PDB to auto-start

SQL> alter pluggable database DB19 open;

SQL> alter session set container=DB19;

SQL> @?/rdbms/admin/noncdb_to_pdb.sql

SQL> alter pluggable database DB19 close;

SQL> alter pluggable database DB19 open;

SQL> select type, message from pdb_plug_in_violations

     where name='DB19' and status<>'RESOLVED';

SQL> select open_mode, restricted from v$pdbs;

SQL> alter pluggable database DB19 save state;

Convert | noncdb_to_pdb.sql

Requires downtime

• Runtime varies - typically 10-30 min

• Fix for Bug 25809128 is included since 19.9.0 and adds a significant improvement

• Runs only once in the life of a database

• Irreversible

• Re-runnable from 12.2

Fallback| PDB Downgrade 

Downgrade works for CDB/PDB entirely as well as for single/multiple PDBs

• Manual tasks

• catdwgrd.sql in current (after upgrade) environment

• catrelod.sql in previous (before upgrade) environment

• Don't change COMPATIBLE

• datapatch must roll back SPUs/PSUs/BPs manually

MOS Note: 2172185.1

How to Downgrade a Single Pluggable Oracle Database ( PDB ) to previous release

Migration | Last Words

Every migration 

• Is an architectural change 

• Requires downtime 

• Requires a fallback 

• Ends with a backup

How to migrate a non pluggable database that uses TDE to pluggable database ?

 (Doc ID 1678525.1)

Data Guard | Migration Options 

It is possible to preserve the standby database when you migrate from non-CDB to PDB

Special attention is needed 

You don't have to rebuild your standby database but you might find it is the easiest solution.

Follow Doc - Multitenant Migration