Infrastructure at your Service

Franck Pachot

Service “696c6f76656d756c746974656e616e74” has 1 instance(s).

By Franck Pachot

.
Weird title, isn’t it? That was my reaction when I did my first ‘lsnrctl status’ in 12.2: weird service name… If you have installed 12.2 multitenant, then you have probably seen this strange service name registered in your listener. One per PDB. It is not a bug. It is an internal service used to connect to the remote PDB for features like Proxy PDB. This name is the GUID of the PDB which makes this service independent of the name or the physical location of the PDB. You can use it to connect to the PDB, but should not. It is an internal service name. But on a lab, let’s play with it.

CDB

I have two Container Databases on my system:

18:01:33 SQL> connect sys/[email protected]//localhost/CDB2 as sysdba
Connected.
18:01:33 SQL> show pdbs
 
CON_ID  CON_NAME  OPEN MODE  RESTRICTED
------  --------  ---- ----  ----------
2       PDB$SEED  READ ONLY  NO

CDB2 has been created without any pluggable databases (except PDB$SEED of course).

18:01:33 SQL> connect sys/[email protected]//localhost/CDB1 as sysdba
Connected.
18:01:33 SQL> show pdbs
 
CON_ID  CON_NAME  OPEN MODE   RESTRICTED
------  --------  ---- ----   ----------
2       PDB$SEED  READ ONLY   NO
4       PDB1      READ WRITE  NO

CDB1 has one pluggable database PDB1.

PDB1 has its system files in /u01/oradata/CDB1/PDB1/ and I’ve a user tablespace datafiles elsewhere:

18:01:33 SQL> select con_id,file_name from cdb_data_files;
CON_ID  FILE_NAME
------  -------------------------------------
1       /u01/oradata/CDB1/users01.dbf
1       /u01/oradata/CDB1/undotbs01.dbf
1       /u01/oradata/CDB1/system01.dbf
1       /u01/oradata/CDB1/sysaux01.dbf
4       /u01/oradata/CDB1/PDB1/undotbs01.dbf
4       /u01/oradata/CDB1/PDB1/sysaux01.dbf
4       /u01/oradata/CDB1/PDB1/system01.dbf
4       /u01/oradata/CDB1/PDB1/USERS.dbf
4       /var/tmp/PDB1USERS2.dbf

Both are registered to the same local listener:

SQL> host lsnrctl status
 
LSNRCTL for Linux: Version 12.2.0.1.0 - Production on 07-APR-2017 18:01:33
 
Copyright (c) 1991, 2016, Oracle.  All rights reserved.
 
Connecting to (ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521))
STATUS of the LISTENER
------------------------
Alias                     LISTENER
Version                   TNSLSNR for Linux: Version 12.2.0.1.0 - Production
Start Date                07-APR-2017 07:53:06
Uptime                    0 days 10 hr. 8 min. 27 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Log File         /u01/app/oracle/diag/tnslsnr/VM104/listener/alert/log.xml
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=VM104)(PORT=1521)))
Services Summary...
Service "4aa269fa927779f0e053684ea8c0c27f" has 1 instance(s).
  Instance "CDB1", status READY, has 1 handler(s) for this service...
Service "CDB1" has 1 instance(s).
  Instance "CDB1", status READY, has 1 handler(s) for this service...
Service "CDB1XDB" has 1 instance(s).
  Instance "CDB1", status READY, has 1 handler(s) for this service...
Service "CDB2" has 1 instance(s).
  Instance "CDB2", status READY, has 1 handler(s) for this service...
Service "CDB2XDB" has 1 instance(s).
  Instance "CDB2", status READY, has 1 handler(s) for this service...
Service "pdb1" has 1 instance(s).
  Instance "CDB1", status READY, has 1 handler(s) for this service...
The command completed successfully

Each container database declares its db_unique_name as a service: CDB1 and CDB2, with an XDB service for each: CDB1XDB and CDB2XDB, each pluggable database has also its service: PDB1 here. This is what we had in 12.1 but in 12.2 there is one more service with a strange name in hexadecimal: 4aa269fa927779f0e053684ea8c0c27f

Connect to PDB without a service name?

Want to know more about it? Let’s try to connect to it:

SQL> connect sys/[email protected](DESCRIPTION=(CONNECT_DATA=(SERVICE_NAME=4aa269fa927779f0e053684ea8c0c27f))(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.78.104)(PORT=1521))) as sysdba
Connected.
SQL> select sys_context('userenv','cdb_name'), sys_context('userenv','con_name'), sys_context('userenv','service_name') from dual;
 
SYS_CONTEXT('USERENV','CDB_NAME')  SYS_CONTEXT('USERENV','CON_NAME')  SYS_CONTEXT('USERENV','SERVICE_NAME')
---------------------------------  ---------------------------------  -------------------------------------
CDB1                               PDB1                               SYS$USERS

With this service, I can connect to the PDB1 but the service name I used in the connection string is not a real service:

SQL> select name from v$services;
 
NAME
----------------------------------------------------------------
pdb1
 
SQL> show parameter service
 
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
service_names                        string      CDB1

The documentation says that SYS$USERS is the default database service for user sessions that are not associated with services so I’m connected to a PDB here without a service.

GUID

The internal service name is the GUID of the PDB, which identifies the container even after unplug/plug.

SQL> select pdb_id,pdb_name,con_uid,guid from dba_pdbs;
 
PDB_ID  PDB_NAME  CON_UID     GUID
------  --------  -------     ----
4       PDB1      2763763322  4AA269FA927779F0E053684EA8C0C27F

Proxy PDB

This internal service has been introduced in 12cR2 for Proxy PDB feature: access to a PDB through another one, so that you don’t have to change the connection string when you migrate the PDB to another server.

I’ll create a Proxy PDB in CDB2 to connect to PDB1 which is in CDB1. This is simple: create a database link for the creation of the Proxy PDB which I call PDB1PX1:

18:01:33 SQL> connect sys/[email protected]//localhost/CDB2 as sysdba
Connected.
18:01:33 SQL> show pdbs
 
CON_ID  CON_NAME  OPEN MODE  RESTRICTED
------  --------  ---- ----  ----------
2       PDB$SEED  READ ONLY  NO
 
18:01:33 SQL> create database link CDB1 connect to system identified by oracle using '//localhost/CDB1';
Database link CDB1 created.
 
18:01:38 SQL> create pluggable database PDB1PX1 as proxy from [email protected]
             file_name_convert=('/u01/oradata/CDB1/PDB1','/u01/oradata/CDB1/PDB1PX1');
 
Pluggable database PDB1PX1 created.
 
18:02:14 SQL> drop database link CDB1;
Database link CDB1 dropped.

The Proxy PDB clones the system tablespaces, and this is why I had to give a file_name_convert. Note that the user tablespace datafile is not cloned, so I don’t need to convert the ‘/var/tmp/PDB1USERS2.dbf’. The dblink is not needed anymore once the Proxy PDB is created, as it is used only for the clone of system tablespaces. The PDB is currently in mount.

18:02:14 SQL> connect sys/[email protected]//localhost/CDB2 as sysdba
Connected.
18:02:14 SQL> show pdbs
 
CON_ID  CON_NAME  OPEN MODE  RESTRICTED
------  --------  ---- ----  ----------
2       PDB$SEED  READ ONLY  NO
3       PDB1PX1   MOUNTED

The system tablespaces are there (I’m in 12.2 with local undo which is required for Proxy PDB feature)

18:02:14 SQL> select con_id,file_name from cdb_data_files;
 
CON_ID  FILE_NAME
------  ---------
1       /u01/oradata/CDB2/system01.dbf
1       /u01/oradata/CDB2/sysaux01.dbf
1       /u01/oradata/CDB2/users01.dbf
1       /u01/oradata/CDB2/undotbs01.dbf

I open the PDB

18:02:19 SQL> alter pluggable database PDB1PX1 open;
Pluggable database PDB1PX1 altered.

connect

I have now 3 ways to connect to PDB1: with the PDB1 service, with the internal service, and through the Proxy PDB service.
I’ve tested the 3 ways:


18:02:45 SQL> connect demo/[email protected]//localhost/PDB1
18:02:56 SQL> connect demo/[email protected]//localhost/PDB1PX1
18:03:06 SQL> connect demo/[email protected]//localhost/4aa269fa927779f0e053684ea8c0c27f

and I’ve inserted each time into a DEMO table the information about my connection:

SQL> insert into DEMO select '&_connect_identifier' "connect identifier", current_timestamp "timestamp", sys_context('userenv','cdb_name') "CDB name", sys_context('userenv','con_name') "con name" from dual;

Here is the result:

connect identifier                            timestamp                        CDB name  container name
------------------                            ---------                        --------  --------------
//localhost/PDB1                              07-APR-17 06.02.50.977839000 PM  CDB1      PDB1
//localhost/PDB1PX1                           07-APR-17 06.03.01.492946000 PM  CDB1      PDB1
//localhost/4aa269fa927779f0e053684ea8c0c27f  07-APR-17 06.03.11.814039000 PM  CDB1      PDB1

We are connected to the same databases. As for this test I’m on the same server with same listener, I can check what is logged in the listener log.

Here are the $ORACLE_BASE/diag/tnslsnr/$(hostname)/listener/alert/log.xml entries related to my connections.

//localhost/PDB1

When connecting directly to PDB1 the connection is simple:


<msg time='2017-04-07T18:02:45.644+02:00' org_id='oracle' comp_id='tnslsnr'
 type='UNKNOWN' level='16' host_id='VM104'
 host_addr='192.168.78.104' pid='1194'>
 <txt>07-APR-2017 18:02:45 * (CONNECT_DATA=(SERVICE_NAME=PDB1)(CID=(PROGRAM=java)(HOST=VM104)(USER=oracle))) * (ADDRESS=(PROTOCOL=tcp)(HOST=127.0.0.1)(PORT=27523)) * establish * PDB1 * 0
 </txt>
</msg>

I am connecting with SQLcl which is java: (PROGRAM=java)

//localhost/PDB1PX1

When connecting through the Proxy PDB I see the connection to the Proxy PDBX1:


<msg time='2017-04-07T18:02:56.058+02:00' org_id='oracle' comp_id='tnslsnr'
 type='UNKNOWN' level='16' host_id='VM104'
 host_addr='192.168.78.104' pid='1194'>
 <txt>07-APR-2017 18:02:56 * (CONNECT_DATA=(SERVICE_NAME=PDB1PX1)(CID=(PROGRAM=java)(HOST=VM104)(USER=oracle))) * (ADDRESS=(PROTOCOL=tcp)(HOST=127.0.0.1)(PORT=27524)) * establish * PDB1PX1 * 0
 </txt>
</msg>

This is the java connection. But I can also see the connection to the remote PDB1 from the Proxy PDB


<msg time='2017-04-07T18:03:01.375+02:00' org_id='oracle' comp_id='tnslsnr'
 type='UNKNOWN' level='16' host_id='VM104'
 host_addr='192.168.78.104' pid='1194'>
 <txt>07-APR-2017 18:03:01 * (CONNECT_DATA=(SERVICE_NAME=4aa269fa927779f0e053684ea8c0c27f)(CID=(PROGRAM=oracle)(HOST=VM104)(USER=oracle))) * (ADDRESS=(PROTOCOL=tcp)(HOST=192.168.78.104)(PORT=16787)) * establish * 4aa269fa927779f0e053684ea8c0c27f * 0
 </txt>
</msg>

Here the program is (PROGRAM=oracle) which is a CDB2 instance process connecting to the CDB1 remote through the internal service.

//localhost/4aa269fa927779f0e053684ea8c0c27f

When I connect to the internal service, I see the same connection to PDB1’s GUID but from (PROGRAM=java) directly


<msg time='2017-04-07T18:03:06.671+02:00' org_id='oracle' comp_id='tnslsnr'
 type='UNKNOWN' level='16' host_id='VM104'
 host_addr='192.168.78.104' pid='1194'>
 <txt>07-APR-2017 18:03:06 * (CONNECT_DATA=(SERVICE_NAME=4aa269fa927779f0e053684ea8c0c27f)(CID=(PROGRAM=java)(HOST=VM104)(USER=oracle))) * (ADDRESS=(PROTOCOL=tcp)(HOST=127.0.0.1)(PORT=27526)) * establish * 4aa269fa927779f0e053684ea8c0c27f * 0
 </txt>
</msg>

One more…

So each user PDB, in addition to the PDB name and additional services you have defined, registers an additional internal service, whether the PDB is opened our closed. And the fun is that Proxy PDB also register this additional service. Here is my listener status:


Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=VM104)(PORT=1521)))
Services Summary...
Service "4aa269fa927779f0e053684ea8c0c27f" has 1 instance(s).
  Instance "CDB1", status READY, has 1 handler(s) for this service...
Service "4c96bda23b8e41fae053684ea8c0918b" has 1 instance(s).
  Instance "CDB2", status READY, has 1 handler(s) for this service...
Service "CDB1" has 1 instance(s).
  Instance "CDB1", status READY, has 1 handler(s) for this service...
Service "CDB1XDB" has 1 instance(s).
  Instance "CDB1", status READY, has 1 handler(s) for this service...
Service "CDB2" has 1 instance(s).
  Instance "CDB2", status READY, has 1 handler(s) for this service...
Service "CDB2XDB" has 1 instance(s).
  Instance "CDB2", status READY, has 1 handler(s) for this service...
Service "pdb1" has 1 instance(s).
  Instance "CDB1", status READY, has 1 handler(s) for this service...
Service "pdb1px1" has 1 instance(s).
  Instance "CDB2", status READY, has 1 handler(s) for this service...
The command completed successfully

This “4c96bda23b8e41fae053684ea8c0918b” is the GUID of the Proxy PDB.

SQL> select sys_context('userenv','cdb_name'), sys_context('userenv','con_name'), sys_context('userenv','service_name') from dual;
 
SYS_CONTEXT('USERENV','CDB_NAME')
--------------------------------------------------------------------------------
SYS_CONTEXT('USERENV','CON_NAME')
--------------------------------------------------------------------------------
SYS_CONTEXT('USERENV','SERVICE_NAME')
--------------------------------------------------------------------------------
CDB1
PDB1
SYS$USERS

So that’s a fourth way to connect to PDB1: through the internal service of the Proxy PDB.

Then you can immediately imagine what I tried…

ORA-65280

Because the internal service name is used to connect through Proxy PDB, can I create an proxy for the proxy?

18:03:32 SQL> create pluggable database PDB1PX2 as proxy from [email protected]
  2   file_name_convert=('/u01/oradata/CDB1/PDB1/PX1','/u01/oradata/CDB1/PDB1PX2');
 
Error starting at line : 76 File @ /media/sf_share/122/blogs/proxypdb.sql
In command -
create pluggable database PDB1PX2 as proxy from [email protected]
 file_name_convert=('/u01/oradata/CDB1/PDB1/PX1','/u01/oradata/CDB1/PDB1PX2')
Error report -
ORA-65280: The referenced pluggable database is a proxy pluggable database.

Answer is no. You cannot nest the Proxy PDB.

So what?

Don’t panic when looking at services registered in the listener. Those hexadecimal service names are expected in 12.2, with one per user PDB. You see them, but have no reason to use them directly. You will use them indirectly when creating a Proxy PDB which makes the location where users connect independent from the physical location of the PDB. Very interesting from migration because client configuration is independent from the migration (think hybrid-cloud). You can use this feature even without the multitenant option. Want to see all multitenant architecture options available without the option? Look at the ITOUG Tech day agenda

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Franck Pachot
Franck Pachot

Principal Consultant / Database Evangelist
 Oracle ACE Director
 Oracle Database OCM 12c certified
 AWS Database Specialty certified
 Oak Table member

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