PLUGGABLE DATABASE : ORACLE 12C
Disclaimer : Content of this blog refers to Andrew speech in the Oracle Open World (OOW 2012) (Oracle Database : OOW 2012) and other material found on net. It is intended for information purposes only for learning. The development and release of these functions including the release dates remain at the sole discretion of Oracle.
Pluggable database is the new feature proposed in Oracle Database 12C which will be released in 2013.
Main drawback with the existing database architecture is a single database server requires memory,process and database files that is core Oracle System dictionary (tables,objects..) i.e Oracle metadata is tightly integrated with the application dictionary i.e tenants metadata, so separate memory,processes,files required for each database (ERP,CRM,DW).
In Oracle Database Server 12C, there is an architectural separation (Split Data Dictionary) between Core Oracle System with User Applications they are loosely coupled. Pluggable Database Architecture consists of
1) Container Database (CDB)
2) Pluggable Database (PDB)
1) Container Database (CDB) : Holds Oracle System dictionary , functionality and metadata required to run the database. Memory and Process required for multiple PDB will be handled by a single CDB.
2) Pluggable Database (PDB) : This holds only user application metadata or customer metadata or dictionary. This has read only permission on oracle dictionary. In cloud each Pluggable Database is analogous to single Customer. There is clean separation between each pluggable database .
As shown in the above image, a single instance of container database support ERP,CRM,DW applications. All pdb's will share memory and process based on oracle resource management capability. Single CDB will support 250 pluggable databases or more.This new feature is compatible with older Oracle databases also .pluggable databases can be plugged or unplugged to the container database at any point of time.
Compared to separate databases pluggable database is highly efficient , 6x less h/w resources and 5x scalable.
Patching and upgrades : Apply patch once then all pluggable databases will be updated. You can clone a PDB within the same CDB or into another CDB. PDBs can also be provisioned very fast as each CDB comes with a “PDB Seed” from where the new PDB can be fast provisioned. So the provisioning becomes very fast.
Redeployment becomes much easier as we can unplug the database from one platform or a CDB version and then plug it into a CDB which is in another platform or version. This will make the upgrade, patching and redeployment efforts much faster! When you upgrade the CDB, all the PDBs will get upgraded. If you would like to control when the PDBs should be upgraded, you can create another CDB version and then unplug from the old release and then plug in to the new database release. All PDB contents are separate from each other PDB so the “separation of duties” works very well as well.
Backup: backingup data present in multiple pdb's is very simple, treat entire database as one and recover all pdb's once or you can restore individual pdb.
Pluggable databases are perfect for SaaS as each pdb is allocated to a customer.
