Creating a New Pluggable Database Using PDB$SEED

Oracle's Multitenant architecture allows a Container Database (CDB) to host multiple Pluggable Databases (PDBs), each acting as a fully independent Oracle database. One of the most common DBA tasks is provisioning a new PDB — and the fastest, cleanest way to do it is by cloning from PDB$SEED, the read-only template PDB that ships with every CDB.

In this guide, we walk through the entire process — from verifying prerequisites to opening and saving the PDB's state across restarts.

What is PDB$SEED?

PDB$SEED is a special, read-only template PDB that Oracle ships with every Container Database. It contains the minimal set of data files and dictionary objects required to seed a new Pluggable Database. When you create a PDB using the default method, Oracle copies PDB$SEED's data files to a new location and bootstraps a fresh PDB from them.

Key characteristics of PDB$SEED:

•        Always in READ ONLY mode — it can never be opened for writes

•        CON_ID = 2 in every CDB (CDB$ROOT = 1, user PDBs start from 3)

•        Patched automatically when you run datapatch on the CDB

•        Serves as the template for CREATE PLUGGABLE DATABASE ... FROM PDB$SEED (the default)

Note: Never attempt to open PDB$SEED in READ WRITE mode. Oracle will reject it, and attempting workarounds can corrupt your CDB.

Step 1 -Verify Prerequisites

Before issuing the CREATE command, confirm your session is connected to CDB$ROOT and that PDB$SEED is healthy.

1. Confirm you are in CDB$ROOT

    Show CON_NAME

2. Confirm this is a CDB

     SELECT NAME, CDB, CON_ID FROM V$DATABASE;

3. List all existing PDBs
        SELECT CON_ID, NAME, OPEN_MODE, RESTRICTED FROM V$PDBS ORDER  BY CON_ID;

4. Verify PDB$SEED is READ ONLY

    SELECT CON_ID, NAME, OPEN_MODE FROM   V$PDBS WHERE  NAME = 'PDB$SEED';

Note: If SHOW CON_NAME returns a PDB name rather than CDB$ROOT, switch back: ALTER SESSION SET CONTAINER = CDB$ROOT;

Step 2 - Create the Pluggable Database

CREATE PLUGGABLE DATABASE TESTPDB1 ADMIN USER TESTPDB1 IDENTIFIED BY "StrongPassword#1"  ROLES = (DBA)  DEFAULT TABLESPACE users DATAFILE '/u01/app/oracle/oradata/TEST/TESTPDB1/users01.dbf' SIZE 250M AUTOEXTEND ON NEXT 50M MAXSIZE UNLIMITED  FILE_NAME_CONVERT = ( '/u01/app/oracle/oradata/TEST/pdbseed/',    '/u01/app/oracle/oradata/TEST/TESTPDB1/');

Step 3 - Open the PDB

Newly created PDB is in MOUNTED state. You must open it explicitly before any connections can be made.

Open the PDB in READ WRITE mode

    ALTER PLUGGABLE DATABASE TESTPDB1 OPEN;

Verify the open mode

    SELECT CON_ID, NAME, OPEN_MODE, RESTRICTED FROM   V$PDBS WHERE  NAME = 'PDB_NAME';

Step 4 - Save the Open State

By default, PDBs return to MOUNTED state when the CDB is restarted. Use SAVE STATE to instruct Oracle to automatically re-open the PDB to its saved mode after every CDB startup.

Persist the open state across CDB restarts
 ALTER PLUGGABLE DATABASE TESTPDB1 SAVE STATE;

Confirm the saved state
    SELECT CON_NAME, STATE FROM   DBA_PDB_SAVED_STATES;

Note: SAVE STATE is the equivalent of adding the PDB to a startup trigger. Always run it after opening a new PDB in production.

Step 5 - Post-Creation Tasks

With the PDB open, switch into it and perform the initial housekeeping tasks before handing it off to the application team.

-- Switch into the new PDB

ALTER SESSION SET CONTAINER = TESTPDB1;

-- Confirm context

SHOW CON_NAME;

-- Review tablespaces

SELECT TABLESPACE_NAME, STATUS, CONTENTS FROM   DBA_TABLESPACES; 

-- Create the application user

CREATE USER app_user IDENTIFIED BY "AppPassword#1"

  DEFAULT TABLESPACE users

  TEMPORARY TABLESPACE temp

  QUOTA UNLIMITED ON users;

 GRANT CONNECT, RESOURCE TO app_user;

 -- Return to CDB root

ALTER SESSION SET CONTAINER = CDB$ROOT;

The table below covers the most frequent errors encountered during PDB creation and their resolutions.

Error Code	Cause	Fix
ORA-65012	PDB name already exists	Choose a different name or drop the existing PDB
ORA-17537	Wrong file path	Verify FILE_NAME_CONVERT paths exist on the OS
ORA-65016	FILE_NAME_CONVERT required	Set DB_CREATE_FILE_DEST or specify FILE_NAME_CONVERT
ORA-01109	PDB not open	Run ALTER PLUGGABLE DATABASE pdb_name OPEN
ORA-65040	Not in CDB root	Run ALTER SESSION SET CONTAINER = CDB$ROOT first

Key Takeaways

• PDB$SEED is the read-only seed template — never open it in READ WRITE mode
• Always run from CDB$ROOT with SYSDBA privileges when creating PDBs
• FILE_NAME_CONVERT is mandatory unless OMF (DB_CREATE_FILE_DEST) is configured
• Newly created PDBs are in MOUNTED state — open them explicitly with ALTER PLUGGABLE DATABASE ... OPEN
• Always run SAVE STATE in production so PDBs survive CDB restarts automatically
• Each PDB shares the CDB's redo, undo, and TEMP — but owns its own data files.

Caution: Your use of any information or materials on this Blog is entirely at your own risk. It is provided for educational purposes only.