Oracle - PDB$SEED
Can I have more than one PDB$SEED?
No, one CDB can have and only have one PDB$SEED. But, we can put a database to read only as SEED database, and clone from it.
Can I close PDB$SEED?
By default, PDB$SEED cannot be modified and close
SQL> alter pluggable database PDB$SEED close;
alter pluggable database PDB$SEED close
*
ERROR at line 1:
ORA-65017: seed pluggable database may not be dropped or altered
SQL> alter pluggable database all close;
Pluggable database altered.
SQL> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ ONLY NO
3 HR MOUNTED
But, with dbms_pdb.exec_as_oracle_script, we can do this:
SQL> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ ONLY NO
3 HR MOUNTED
SQL> exec dbms_pdb.exec_as_oracle_script('alter pluggable database PDB$SEED close');
PL/SQL procedure successfully completed.
SQL> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED MOUNTED
3 HR MOUNTED
SQL> exec dbms_pdb.exec_as_oracle_script('alter pluggable database PDB$SEED open');
PL/SQL procedure successfully completed.
SQL> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ WRITE NO
3 HR MOUNTED
SQL> exec dbms_pdb.exec_as_oracle_script('alter pluggable database PDB$SEED close');
PL/SQL procedure successfully completed.
SQL> exec dbms_pdb.exec_as_oracle_script('alter pluggable database PDB$SEED open read only');
PL/SQL procedure successfully completed.
SQL> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ ONLY NO
3 HR MOUNTED
How to modify PDB$SEED?
How To Modify the Common Profile Limit in Multitenant Database? (Doc ID 2328994.1)
alter session set "_oracle_script"=true;
SQL> alter session set container=pdb$seed;
Session altered.
SQL> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ ONLY NO
SQL> alter session set "_oracle_script"=true;
Session altered.
SQL> shutdown immediate;
Pluggable Database closed.
SQL> startup
Pluggable Database opened.
SQL> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ WRITE NO
SQL> create tablespace test datafile size 10M;
Tablespace created.
SQL> shutdown immediate;
Pluggable Database closed.
SQL> startup open read only;
Pluggable Database opened.
SQL> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ ONLY NO
-- after reconnect to cdb
SQL> startup force;
ORACLE instance started.
Total System Global Area 713031680 bytes
Fixed Size 2928488 bytes
Variable Size 520093848 bytes
Database Buffers 184549376 bytes
Redo Buffers 5459968 bytes
Database mounted.
Database opened.
SQL> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ ONLY NO
3 HR MOUNTED
What will happen if the datafile of PDB$SEED missing and how to recreate without backup?
CDB can open, PDB$SEED can open read only if the missing datafile is not SYSTEM/UNDO.
SQL> select file_name from dba_data_files;
select file_name from dba_data_files
*
ERROR at line 1:
ORA-01157: cannot identify/lock data file 13 - see DBWR trace file
ORA-01110: data file 13: '/opt/oracle/oradata/O12102/7DE2B53C634D1689E053291010532345/datafile/o1_mf_test_g6pwnokd_.dbf'
If you don’t clone an new PDB, there is no impact.
There is no simple way to create PDB$SEED with some scripts.
The standard way is recreate a new CDB and unplug from the old cdb and plug into the new one.
Missing PDB$SEED's Datafiles with no backup (Doc ID 2104370.1)
How to create a new PDB$SEED from an existing PDB?
We can use dbms_pdb.exec_as_oracle_script to drop PDB$SEED and clone a new one from an existing PDB
But it is not an documented way.
SQL> exec dbms_pdb.exec_as_oracle_script('alter pluggable database PDB$SEED close');
PL/SQL procedure successfully completed.
SQL> exec dbms_pdb.exec_as_oracle_script('drop pluggable database PDB$SEED including datafiles');
PL/SQL procedure successfully completed.
SQL> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
3 HR MOUNTED
SQL> alter pluggable database hr open;
Pluggable database altered.
SQL> create pluggable database PDB$SEED FROM HR;
Pluggable database created.
SQL> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED MOUNTED
3 HR READ WRITE NO
SQL> alter pluggable database PDB$SEED open;
alter pluggable database PDB$SEED open
*
ERROR at line 1:
ORA-65017: seed pluggable database may not be dropped or altered
SQL> exec dbms_pdb.exec_as_oracle_script('alter pluggable database PDB$SEED open');
PL/SQL procedure successfully completed.
SQL> exec dbms_pdb.exec_as_oracle_script('alter pluggable database PDB$SEED close');
PL/SQL procedure successfully completed.
SQL> exec dbms_pdb.exec_as_oracle_script('alter pluggable database PDB$SEED open read only');
PL/SQL procedure successfully completed.
Do I need to patch PDB$SEED manually?
Patching the PDB$SEED (Doc ID 2038564.1)
PDB$SEED patching is automatically handled through datapatch so we shouldn’t have to manually patch the PDB$SEED.
What can I redefine when create a new PDB from PDB$SEED?
create pluggable database pdb1 admin user ctais2 identified by oracle roles=(dba) parallel 2 default tablespace test datafile size 10M storage unlimited tempfile reuse logging -- file_name_convert # useful is we don't use OMF -- create_file_dest # useful is we don't use OMF -- service_name_convert # there is no other service in the PDB$SEED -- path_prefix # used to restrict the path of directory objects -- standbys # used to exclude this PDB in the standby side -- user_tablespaces # not useful, PDB$SEED doesn't have other tablespaces -- host= port= # not useful, we create from PDB locally. /
