A lead CDB is the central location for monitoring and managing the CDBs in the fleet. A CDB fleet provides the database infrastructure for scalability and centralized management of many CDBs.
Designate one CDB in the fleet to be the lead CDB by setting its LEAD_CDB database property to TRUE. The other CDBs in the fleet point to the lead CDB by setting the LEAD_CDB_URI database property. After you configure the CDB fleet, PDB information from the various CDBs is synchronized with the lead CDB. All PDBs in the CDBs are now “visible” in the lead CDB, enabling you to access the PDBs in the fleet as a single, logical CDB from the lead CDB.
The following figure shows a CDB fleet consisting of CDB1, CDB2, and CDB3. The lead CDB is CDB1. CDB2_hrpdb, which resides in CDB2, is visible in CDB1. CDB3_hrpdb, which resides in CDB3, is also visible in CDB1.
In this example, we are using 2 CDBs
| CDB | PDBs |
| CDB18C | PDB$SEED |
| PDB18C1 | |
| PDB18C2 | |
| PDB18CSNAP | |
| CDBNEW | PDB$SEED |
| PDB18CFLEET |
Setting the Lead CDB in a CDB Fleet
Login to CDB18C and make it as LEAD CDB.
SQL> select name from v$database; NAME --------- CDB18C SQL> SELECT PROPERTY_VALUE FROM DATABASE_PROPERTIES WHERE PROPERTY_NAME='LEAD_CDB'; no rows selected SQL> ALTER SESSION SET CONTAINER = CDB$ROOT; Session altered. SQL> ALTER DATABASE SET LEAD_CDB = TRUE; Database altered. SQL> SELECT PROPERTY_VALUE FROM DATABASE_PROPERTIES WHERE PROPERTY_NAME='LEAD_CDB'; PROPERTY_VALUE --------------------- TRUE SQL>
Let’s Check the count of PDBs in CDB18C till now.
SQL> select name from v$database; NAME --------- CDB18C SQL> show pdbs CON_ID CON_NAME OPEN MODE RESTRICTED ---------- ---------- ----------- ----------- 2 PDB$SEED READ ONLY NO 3 PDB18C1 MOUNTED 4 PDB18C2 READ WRITE NO 7 PDB18CSNAP READ WRITE NO
Now login to another CDB i.e NEWCDB and create a database link and also set the LEAD_CDB_URI.
SQL> select name from v$database; NAME --------- NEWCDB SQL> SELECT PROPERTY_VALUE FROM DATABASE_PROPERTIES WHERE PROPERTY_NAME='LEAD_CDB_URI'; no rows selected SQL> CREATE PUBLIC DATABASE LINK lead_link CONNECT TO system IDENTIFIED BY sys USING 'CDB18C'; Database link created. SQL> select name from v$database@lead_link; NAME --------- CDB18C SQL> ALTER DATABASE SET LEAD_CDB_URI = 'dblink:LEAD_LINK'; Database altered. SQL> SELECT PROPERTY_VALUE FROM DATABASE_PROPERTIES WHERE PROPERTY_NAME='LEAD_CDB_URI'; PROPERTY_VALUE -------------------------------------------------------------------------------- dblink:LEAD_LINK SQL>
Let’s Check again the PDBs in CDB18C now.
SQL> select name from v$database; NAME --------- CDB18C SQL> show pdbs CON_ID CON_NAME OPEN MODE RESTRICTED ---------- ---------- ---------- ---------- 2 PDB$SEED READ ONLY NO 3 PDB18C1 MOUNTED 4 PDB18C2 READ WRITE NO 6 PDB18CFLEET MOUNTED 7 PDB18CSNAP READ WRITE NO
As we PDB18CFLEET from NEWCDB container is visible in LEAD CDB i.e CDB18C.
Stay tuned for more articles on Oracle 18c
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