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Connor McDonald

Thanks for the question, Narendra.

Asked: June 06, 2025 - 10:12 am UTC

Last updated: July 10, 2025 - 12:18 pm UTC

Version: 19

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Hello Chris/Connor,

Hope you are doing well.
We are using ExaC@C with 19c databases at work and are exploring whether we can use PDB Snapshot Carousel and/or PDB Snapshot Copy feature.
It might be just me but I am somewhat confused with the "art of possible" while using ASM.
PDB Snapshot Copy Process (Doc ID 2730771.1) appears to suggest that we can use sparse disk group feature on exadata to either create PDB snapshot copy or PDB Snapshot Carousel
However, ORA-65227 during pluggable database snapshot (Doc ID 3024542.1) appears to suggest that the feature is simply not supported in 19c and only available from 21c onwards.

https://www.dbarj.com.br/en/2021/09/creating-a-snapshot-sparse-clone-from-a-different-release-update/ appears to even provide an example of how PDB Snapshot Copy can be used to patch a 19c database.

So are we able to use PDB Snapshot Carousel with ASM Sparse Disk Group in ExaC@C by using Sparse Disk Group feature of ASM only (and not using any file system)? I am confused...

Thanks in advance,
Narendra

and Chris said...

When a PDB Snapshot is made (manually or automatically via the Carousel), it also creates a XML manifest file to describe the snapshot files. In 19c ASM, XML is not a supported file type, so when the carousel creates a snapshot, it tries and fails to write the XML file to ASM. Manual snapshots can be made as you can specify the destination of the XML file.

If you were running your 19c database on ACFS, then the carousel works just fine.

So the TL;DR is PDB Snapshot Carousel is supported as follows:

ASM - 23ai
ACFS - 19c, 21c, 23ai
Exascale - 23ai

Big thanks to Alex Blyth, Exadata PM, for providing this information. We're working on updating the MOS notes to clarify this.

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Comments

Introduction to Monkey Mart

Pedro J. Stearns, July 14, 2025 - 1:41 am UTC

Exploring new database features often feels like navigating uncharted waters, especially with evolving tech like ExaC@C and ASM. I once faced a similar challenge at Monkey Mart when trying to implement a snapshot copy in an Exadata environment, only to hit compatibility roadblocks that weren’t clearly documented. The mix of sparse disk groups and version constraints can be really tricky to unravel, particularly when official docs provide conflicting advice. It’s crucial to test thoroughly before relying on these snapshot features in production.


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