Forum Discussion

Kiran_Holi's avatar
Kiran_Holi
Copper Contributor
Feb 20, 2024

Azure application insights workspace based migration related questions

Hello,

We have migrated our classic application insights instances to workspace based successfully.

 

After migration, I see that new data post migration is getting stored in linked log analytics workspace (which is expected) and also new data is getting stored at classic application insights as well.

 

As per your documentation, after migration, old data will remain in classic application insight and new data will be stored in linked log analytics workspace.

https://learn.microsoft.com/en-us/azure/azure-monitor/app/convert-classic-resource

 

Questions

  • Why new data is still getting stored in old classic app insights after migration? This is not mentioned in https://learn.microsoft.com/en-us/azure/azure-monitor/app/convert-classic-resource.
    • Let us assume that it is getting stored to support the backward compatibility. How many days this is supported after migration?
  • We have existing powerbi reports which are pulling data from classic application insights. After migration, let us suppose if I want some data from old app insights and some from new app insights, in this case, I have to write two separate queries and combine the results. Is my understanding correct?

2 Replies

  • Laraib's avatar
    Laraib
    Copper Contributor
    Feb 20, 2026

    After migrating to workspace-based Application Insights, it's normal for new data to still show up in the classic Application Insights temporarily due to backward compatibility. This should stop after a transition period, but Microsoft hasn’t specified how long this lasts.

     

    For your Power BI reports, yes, you'll need to write separate queries for the old and new data and combine them in Power BI.

  • Kidd_Ip's avatar
    Kidd_Ip
    MVP
    Feb 20, 2026

    I tried to summarize the case below:

     

    • During the migration process, new telemetry may continue to appear in the classic Application Insights resource for up to 24 hours.
    • After the migration cutover is complete, all subsequent telemetry is ingested exclusively into the linked Log Analytics workspace.
    • Historical data remains accessible in the classic Application Insights resource until it reaches the end of its configured retention period.
    • To analyze both pre‑migration and post‑migration data, queries must be executed against each source separately and the results combined.