Multitenant Architecture And RAC Database

• Pradip
• 25 Jul, 2025
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• 3 Mins Read

Multitenant Architecture And RAC Database

Overview of Oracle Multitenant Architecture:

Oracle’s Multitenant Architecture was
introduced with Oracle Database 12c. It allows a single container database (CDB) to host
multiple pluggable databases (PDBs). This architecture simplifies database consolidation
and management, reducing costs and improving resource utilization.

1. Container Database (CDB): The CDB is the main structure that contains one or
   more pluggable databases (PDBs). The CDB has a root container (CDB$ROOT) that
   contains Oracle metadata and the seed PDB (PDB$SEED) used as a template for
   creating new PDBs.
2. Pluggable Database (PDB): A PDB is a fully functional Oracle database that is
   hosted inside the CDB. Each PDB has its own set of data files, tablespaces,
   schemas, and other resources.
3. Benefits of Multitenant Architecture:
   o Resource Efficiency: Multiple databases share the memory, storage, and
   processes of the CDB, reducing resource overhead.
   o Rapid Provisioning: PDBs can be quickly created or cloned, allowing for
   rapid development and deployment.
   o Centralized Management: All PDBs within a CDB are managed as a single
   entity, simplifying operations such as backup, recovery, and patching.

Oracle Real Application Clusters (RAC):

Oracle RAC allows multiple instances of
Oracle Database to run on different servers while accessing the same database, providing
high availability, scalability, and load balancing.
RAC Architecture:
o Shared Disk Architecture: All RAC instances share the same database files,
stored on shared storage accessible by all nodes.
o Clusterware: Oracle Clusterware manages the availability of the nodes and
instances, including starting, stopping, and monitoring the instances across
the cluster.
o Cache Fusion: RAC instances communicate with each other via high-speed
interconnects to coordinate memory and data access, ensuring data
consistency and preventing data corruption.

Combining Multitenant and RAC:

The combination of Multitenant Architecture with RAC creates a powerful environment for
enterprise-grade cloud and on-premises deployments, offering both consolidation and high
availability.
 Deployment Considerations:
o PDB Mobility: PDBs can be moved between RAC nodes for load balancing,
failover, or to optimize resource usage.
o Scalability: RAC provides horizontal scalability, allowing new nodes to be
added to the cluster, while Multitenant provides vertical scalability by allowing
more PDBs to be added to the CDB.
o High Availability: With RAC, if a node fails, the database continues to run on
other nodes, ensuring continuous availability of the PDBs hosted in the CDB.
o Patch and Upgrade Flexibility: PDBs allow for patching and upgrading
individual databases independently within the CDB, while RAC ensures that
these operations can occur without downtime.

Benefits of Using Multitenant and RAC Together:

1. Consolidation with High Availability: You can consolidate many databases into a
   single CDB while benefiting from the fault tolerance and high availability of RAC.
2. Cost Efficiency: Combining the resource efficiency of Multitenant with the shared
   infrastructure of RAC reduces the total cost of ownership.
3. Disaster Recovery: RAC can be combined with Oracle Data Guard to provide
   disaster recovery solutions for multitenant databases, protecting both the CDB and
   its PDBs.

Example Scenarios:

1.  Cloud Deployments: Multitenant with RAC is ideal for cloud environments, offering
   both elasticity (scaling in or out) and isolation (with each PDB acting as a separate
   tenant).
2. Service Consolidation: Large organizations with many databases (e.g., for different
   departments or clients) can consolidate their databases into fewer CDBs, with RAC
   providing the availability and scalability needed for critical services.

Best Practices:

1. Load Balancing: Ensure that workloads are properly balanced across RAC nodes to
   avoid performance bottlenecks.
2. Monitoring and Tuning: Use Oracle Enterprise Manager and other tools to monitor
   both the CDB and individual PDBs for performance and availability.
3. Backup Strategy: Configure RMAN to perform backups at the CDB level, with
   specific attention to ensuring that PDB-level backup and recovery requirements are
   met.