Why should We use multitenant databases?
- Rapid provisioning (Via clones)
- Online PDB relocate (using DB link)
- Sharing background process
- Sharing SGA
- Minimize Capex and Opex
- Single Backup for CDB
- Automatically Standby
- Perform rapid upgrades
- Reference data in a different CDB
- Isolate grants within PDBs
- Refreshable clone - read-only clone that can periodically synchronize with its source PDB
- Snapshot copy PDB - this PDB cannot be unplugged from the CDB root or application root
- CDB -> container database -> DBA point of view
- PDB -> pluggable database -> Application point of view
- Many PDBs can be plugged into a single Multitenant CDB.
- The system container includes the root CDB and all PDBs in the CDB
- An application container consists of exactly one application root, and the PDBs plugged into this root.
- If a PDB belongs to an application container, then it is an application PDB. An application seed is an optional application PDB.
- A CDB administrator manages the CDB itself.
- An application container administrator manages the application container
- An application PDB administrator manages the PDB's within the application container
- A PDB administrator manages PDB outside the container
How Hot clones works?
- Apply redo to catchup the source and apply undo to rollback uncommitted transactions.
Seed -> system,sysaux,temp,undo
CDB$ROOT (oracle system Metadata only - Exactly one) -> PDB$SEED (template - cannot drop), PDB's
- SYS is a common user in the CDB. Every PDB is owned by SYS.
- By default, a user connected to one PDB must use database links to access objects in a different PDB
- To open the PDB, you must start the respective service.
- To stop the PDB,
ALTER PLUGGABLE DATABASE PDB_NAME CLOSE IMMEDIATE;COL NAME FORMAT A15
show conn_name
SELECT NAME, CON_ID, DBID, CON_UID, GUID FROM V$CONTAINERS ORDER BY CON_ID;
select con_id,username,default_tablespace,common from cdb_users;
Select PDB_NAME from DBA_PDBS;
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