Mirroring SQL Server - New tables added via Fabric REST API cause full mirroring of all tables

[Lukas_K]

Hi all,

I'm using the Microsoft Fabric REST API to manage mirrored databases. When I add new tables via the updateDefinition API call, Fabric unexpectedly enables mirroring for all available tables, not just the ones explicitly listed in my mountedTables payload.

Here’s what I do:

• I fetch the current definition using getDefinition

• I update the mountedTables array to include one or more additional tables

• I send the updated definition back using updateDefinition

Even though I only include a subset of tables in mountedTables, after the API call, the Fabric UI shows that all tables are being mirrored, including ones I never selected.

This does not happen when I manually add tables via the UI — only when using the API.

Questions:

• Is this a known issue with the REST API?

• Is there a recommended way to add new tables to an existing mirrored DB without triggering mirroring for all tables?

Thanks in advance!

[v-sdhruv]

Hi @Lukas_K ,

I just wanted to check in and ask if the issue you were facing has been resolved. If not, we’d be happy to assist further—please let us know how we can help.

Looking forward to your update!

Thank you

[v-sdhruv]

Hi @Lukas_K ,
Just wanted to check if you had the opportunity to review the suggestions provided?
If the response has addressed your query, please accept it as a solution so that other members can easily find it.
Thank You

[v-sdhruv]

Hi @Lukas_K ,

This behavior—where all tables are mirrored after an updateDefinition call—is a known issue. When new tables are added via the REST API, the UI reflects mirroring for all available tables, even if only a subset was specified 

This does not happen when tables are added manually via the UI, suggesting a discrepancy between the API's behavior and the UI logic.
1.Ensure your API calls include the preview=true parameter to avoid unintended behavior due to response format changes
2.Validate whether your integration is parsing the response correctly. If it expects an array but receives a JSON object with a value property, it might misinterpret the payload.
3.Until the API behavior is stabilized, consider using the UI for adding tables to avoid triggering full mirroring.

Additionally, you might want to check out-

Troubleshoot Fabric mirrored databases

Hope this helps!

If the response has addressed your query, please accept it as a solution  so that other members can easily find it.
Thank you.