In an Oracle Multitenant configuration, the SID_NAME in a Pluggable Database (PDB) setup differs from traditional standalone databases. Here’s how it works in general:

1. Understanding SID_NAME in a PDB Setup

• The SID_NAME in listener.ora is always associated with the Container Database (CDB), not individual PDBs.
• Pluggable Databases (PDBs) do not have a unique SID. Instead, they are accessed via a service name.

2. Typical listener.ora for a Multitenant Database

Example listener.ora configuration for a CDB with PDBs:

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = westdb)(PORT = 1521))
    )
  )

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (GLOBAL_DBNAME = west.alexlima.com)
      (ORACLE_HOME = /u01/app/oracle/product/19c/dbhome_1)
      (SID_NAME = west)  # Always refers to the CDB
    )
  )

• SID_NAME = west → This is the Container Database (CDB) SID.
• PDBs do not have a SID in listener.ora but are accessed via service names.

3. How to Connect to a PDB

To connect to a specific Pluggable Database (PDB), you need its service name, not a SID.

Find the PDB Service Name

Log into SQL*Plus as SYSDBA and run:

SHOW PARAMETER service_names;

or:

SELECT name, pdb, con_id FROM v$services;

Example Output

NAME         PDB         CON_ID
------------ ---------- ------
CDB$ROOT     CDB$ROOT    1
PDB1_SVC     PDB1        3
PDB2_SVC     PDB2        4

• The CDB SID is west.
• The PDBs are accessed via PDB1_SVC, PDB2_SVC, etc.

TNS Entry for a PDB

If using a tnsnames.ora file:

PDB1_CONN =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = westdb)(PORT = 1521))
    (CONNECT_DATA =
      (SERVICE_NAME = PDB1_SVC)
    )
  )

To connect:

sqlplus user/password@PDB1_CONN

4. Dynamic Registration of PDB Services

Oracle automatically registers PDB services with the listener when the database starts. You can force registration manually:

ALTER SYSTEM REGISTER;

If the PDB service is missing in lsnrctl status, check:

SELECT name FROM dba_services WHERE pdb = 'PDB1';

If necessary, manually add a service:

exec DBMS_SERVICE.CREATE_SERVICE('NEW_PDB_SVC', 'NEW_PDB_SVC');
ALTER SYSTEM SET SERVICE_NAMES='NEW_PDB_SVC' SID='*' SCOPE=BOTH;

5. Summary

Component	Identified By	Example
CDB (Container Database)	SID_NAME in listener.ora	west
PDB (Pluggable Database)	SERVICE_NAME	PDB1_SVC, PDB2_SVC
Connection to PDB	Use SERVICE_NAME	sqlplus user/password@westdb:1521/PDB1_SVC

Key Takeaways

• CDB has a SID, but PDBs use service names.
• PDBs are not listed in listener.ora; they register dynamically.
• Use SHOW PARAMETER service_names; to check PDB service names.

About Pluggable Databases

https://docs.oracle.com/en/cloud/paas/base-database/about-pdb/index.html