Managed table conversion and vacuum

Davide — Wed, 23 Sep 2026 09:27:31 GMT

Hello everyone,

I am looking for clarification about the 14-day rollback period after converting an external table to a managed table using:

ALTER TABLE <table_name> SET MANAGED

Databricks documentation states that the conversion can be rolled back within 14 days. It also says that, after this period, Predictive Optimization or a manual VACUUM can delete data from the old external location to avoid unnecessary storage costs.

I would appreciate clarification on these scenarios:

Running VACUUM before day 14
If I run VACUUM before the 14-day rollback period ends, does it affect only files in the new managed-table location? Or can it also delete files from the original external location?
Retention period shorter than 14 days
If delta.deletedFileRetentionDuration is set to less than 14 days, for example 7 days:
- Does the rollback window become 7 days?
- If I run VACUUM on day 8, could it delete data needed for rollback, or it will just affects the data in the managed location?
Retention period longer than 14 days
If delta.deletedFileRetentionDuration is set to more than 14 days, for example 20 days:
- Does the rollback window remain 14 days or extend to 20 days?
- If I run VACUUM on day 16, could it delete files from the original external location?

My assumptions are that the rollback period is fixed to 14 days so, if you run vacuum before that period will not touch the data in the external location no matter the retention-days. If the retention is more than 20 days and if I run a vacuum or PO kicks in, the data in old location will be deleted.

Has anyone tested these cases or received clarification from Databricks? I could not find details about how the rollback period interacts with delta.deletedFileRetentionDuration, manual VACUUM, and Predictive Optimization.

Thanks for any guidance.

Re: Managed table conversion and vacuum

Isaac_18 — Mon, 02 Nov 2026 14:39:16 GMT

Hi @Davide, this thread never got a reply, but you asked the same thing in SET MANAGED and rollback in relation to VACUUM and posted your test result there, so I'm linking it for anyone who lands here first.

Short version: the 14-day rollback window is its own fixed retention for the old external copy. Your test showed that delta.deletedFileRetentionDuration doesn't shorten it or stretch it.

What the docs spell out:

Databricks keeps the data in the old external location for 14 days so you can roll back.
Rolling back is ALTER TABLE ... UNSET MANAGED inside that window (DBR 17.3 LTS+ or serverless). Writes made to the managed location after conversion are kept, and you need to restart any streaming jobs afterwards.
After 14 days, predictive optimization deletes the old external data. If predictive optimization is off, you run VACUUM on the converted table yourself to reclaim it.

-- roll back within 14 days
ALTER TABLE main.sales.orders UNSET MANAGED;

-- check whether predictive optimization will clean up for you
DESCRIBE TABLE EXTENDED main.sales.orders;  -- look for the Predictive Optimization row

If rollback really matters for a table, I'd still keep manual VACUUM jobs off it for the full 14 days. It costs you nothing and you never have to wonder.

topic Managed table conversion and vacuum in Data Engineering

Managed table conversion and vacuum

Re: Managed table conversion and vacuum