Exadata as Code – PDB Snapshot Cloning

As follow up to the Exadata as Code post, today I’m going to focus on one of the latest features added to our automation: PDB Snapshot Cloning.

PDB snapshot cloning is one of the best development options to offers in a CI/CD project. In an Exadata environment there are special requirements to implement before start using this technology: Sparse Grid Disks and Sparse ASM Disk Group ( description and step-by-step example is available here).

On Exadata, the PDB Snapshot beneficial of all Smart features including offload capabilities, with in addition space- and time-efficient provisioning.

After this brief introduction let’s see how the PDB Snapshot Cloning has been implemented on our Exadata as Code automation.

Exadata Sparse Storage Automation

Select the Oracle Container Database (CDB) where the PDB Snapshot Cloning should be activated, and with One-click provisioning the Sparse Grid disks and Sparse ASM disk group are created.

After the initial provisioning, the automation starts monitoring the space usage, automatically resizing it (increasing/decreasing) when necessary.

Automated storage lifecycle management

PDB Snapshot Cloning Automation

Same principle applies to the different PDB actions: One-click Provisioning/Decommissioning of the PDB Test Master and PDB Snapshot.

Those features are exposed via UI or API to the application developers, making them autonomous on the management of such space efficient database environment.

PDB Snapshot lifecycle management

Oracle DB stored on ASM vs ACFS

Nowadays a new Oracle database environment with Grid Infrastructure has three main storage options:

  1. Third party clustered file system
  2. ASM Disk Groups
  3. ACFS File System

While the first option was not in scope, this blog compares the result of the tests between ASM and ACFS, highlighting when to use one or the other to store 12c NON-CDB or CDB Databases.

The tests conducted on different environments using Oracle version July PSU have shown controversial results compared to what Oracle  is promoting for the Oracle Database Appliance (ODA) in the following paper: “Frequently Asked Questions Storing Database Files in ACFS on Oracle Database Appliance


Outcome of the tests

ASM remains the preferred option to achieve the best I/O performance, while ACFS introduces interesting features like DB snapshot to quickly and space efficiently provision new databases.

The performance gap between the two solutions is not negligible as reported below by the  AWR – TOP Timed Events sections of two PDBs, sharing the same infrastructure, executing the same workload but respectively using ASM and ACFS storage:

  • PDBASM: Pluggable Database stored on  ASM Disk Group
  • PDBACFS:Pluggable Database stored on ACFS File System



PDBASM AWR – TOP Timed Events and Other Stats





PDBACFS AWR – TOP Timed Events and Other Stats




Due to the different characteristics and results when ASM or ACFS is in use, it is not possible to give a generic recommendation. But case by case the choise should be driven by business needs like maximum performance versus fast and efficient database clone.