OneLake availability for an eventhouse copies only newly ingested data by default

Ingest and transform streaming data

Answer Correct answer: E — Enabling OneLake availability copies only new data added to the eventhouse; existing data is included only if you explicitly choose 'Apply to existing tables'.

You have a Fabric workspace that contains a Real-Time Intelligence solution and an eventhouse. Users report that from OneLake file explorer, they cannot see the data from the eventhouse. You enable OneLake availability for the eventhouse. What will be copied to OneLake?

only data added to new databases that are added to the eventhouse
only the existing data in the eventhouse
no data
both new data and existing data in the eventhouse
only new data added to the eventhouse Correct Answer

eventhouse onelake availability dp-700 one lake sync fabric eventhouse backfill

Community Votes

75%

25%

75% of anonymous learners picked answer E. Votes are pick records left by other test-takers — they are not the verified answer.

Community Insight

OneLake availability for an eventhouse is opt-in per database/table and, by default, captures only new data going forward; backfilling existing data is a separate, explicit choice.

When you turn on OneLake availability for an eventhouse in Microsoft Fabric, only data added to the eventhouse after the feature is enabled is made available in OneLake; existing tables are not copied unless you explicitly select 'Apply to existing tables'.

Assuming the feature retroactively copies all existing eventhouse data; the default behavior is forward-only new data, and the existing-data option must be turned on deliberately.

Community Discussion (12 comments)

Tuki93 👍 15 Selected: E

Existing tables aren't affected. New tables are made available in OneLake. https://learn.microsoft.com/en-us/fabric/real-time-intelligence/event-house-onelake-availability#how-it-works

IshtarSQL 👍 7 Selected: E

When you enable OneLake availability for an eventhouse in Microsoft Fabric, only new data ingested into the eventhouse will be synced and made available in OneLake.

zxc01 👍 1 Selected: E

We can enable it on both database and table levels. I think Microsoft just want to ask for default settings with them. on database level, default option is "Apply to existing tables" which will map all tables to Onelake but don't include any old data. same issue when we try it on table level though UI.

CMDev 👍 2 Selected: D

The correct answer is: D. both new data and existing data in the eventhouse When you enable OneLake availability for an eventhouse, you have the option to apply this setting to existing tables by selecting the "Apply to existing tables" option. This means that both new data and existing data will be available in OneLake. As stated in the article: "When turning on the feature, you can also choose to apply this option to existing tables by selecting the Apply to existing tables option, to include historic backfill." This explains why both new and existing data will be copied to OneLake. Check this link: https://learn.microsoft.com/en-us/fabric/real-time-intelligence/event-house-onelake-availability#how-it-works

Kiket2ride 👍 1 Selected: D

I think it used to be that only new data was available but documentation now says otherwise: https://learn.microsoft.com/en-us/fabric/real-time-intelligence/event-house-onelake-availability#how-it-works When you turn availability back on, all data is made available in OneLake, including historic backfill. I vote for D then

DarkDerf 👍 2 Selected: E

If we strictly follow the documentation's explanation that only new tables are made available in OneLake, then your choice E. only new data added to the eventhouse is the most precise answer. ✅ Final Answer: E. only new data added to the eventhouse

DarkDerf 👍 1 Selected: D

The correct answer is: D. both new data and existing data in the eventhouse Explanation: When you enable OneLake availability for an eventhouse in Microsoft Fabric, all existing data within the eventhouse, along with any new data added afterward, is copied to OneLake. This ensures that users can access both past and future data through OneLake file explorer. This means that enabling OneLake availability makes the entire dataset in the eventhouse visible in OneLake, not just new data moving forward.

henryphchan 👍 3 Selected: E

Only new data will be loaded to OneLake

Anushareddysri 👍 1 Selected: D

As per the Microsoft document you can enable onelake along with an option of existing tables as well. Here is the reference document. https://learn.microsoft.com/en-us/fabric/real-time-intelligence/event-house-onelake-availability

h2o_molecule 👍 2 Selected: D

You can turn on OneLake availability at the database or table level. When enabled at the database level, all new tables and their data are made available in OneLake. When turning on the feature, you can also choose to apply this option to existing tables by selecting the Apply to existing tables option.

e0f0ce6 👍 2 Selected: E

I think E is correct: https://learn.microsoft.com/en-us/fabric/real-time-intelligence/event-house-onelake-availability

QAZdbarhate12345678 👍 3 Selected: D

The correct answer is: D. both new data and existing data in the eventhouse When you enable OneLake availability for the eventhouse, both the existing data and any new data added to the eventhouse will be copied to OneLake. This allows users to access the eventhouse data from OneLake file explorer.

Comments & Corrections

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Expert Analysis

Why the Answer Is Correct

Microsoft Fabric documentation for eventhouse OneLake availability states that when you enable the feature, new tables (and their data) created in the database are automatically made available in OneLake. To also include existing tables you must explicitly select the 'Apply to existing tables' option at enablement time. Because the question only says you enable the feature without selecting backfill, the correct outcome is that only new data added to the eventhouse is copied to OneLake.

Why the Other Options Are Wrong

Option A describes data from brand-new databases added later, not the steady-state behavior of enabling the feature on the existing eventhouse. Option B (only existing data) and D (both existing and new) both assume the optional backfill was applied, which the scenario does not state. Option C (no data) contradicts the feature entirely.

Community Comment Notes

The community was split (E 75 vs D 25). The top-voted comment (Tuki93, 15 likes) notes existing tables are not affected and only new tables are made available, matching E. Several later comments cite the 'Apply to existing tables' toggle as the reason D could be argued, but that toggle is an explicit, unmentioned step, so the precise default answer is E.

Official Reference

https://learn.microsoft.com/en-us/fabric/real-time-intelligence/event-house-onelake-availability

Exam Strategy

When a question mentions enabling OneLake availability for an eventhouse but does not explicitly state that you selected the 'Apply to existing tables' option, assume no backfill occurred. The default behavior only syncs newly created tables and their data to OneLake, making 'only new data' the correct choice over options suggesting existing data is included.

Frequently Asked Questions

Does enabling OneLake availability copy existing tables?

No, it only syncs new tables created after enabling. You must explicitly select 'Apply to existing tables' to backfill old data.

What happens if I don't see data in OneLake Explorer?

The feature was likely enabled without the backfill option. Only new data added to the eventhouse is automatically copied to OneLake.

Related Analysis

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