Migration from MMA to DCR table: how to rename a column?

Question

I'm trying to migrate a Custom log table (classic) to the new DCR-based tables. The old MMA table has some fields that start with underscore (_) which are not allowed in the new DCR-based tables, so I'm getting an error with the API POST command recommended by the documentation.

How should I proceed in this case?

Documentation for reference: https://learn.microsoft.com/en-us/azure/azure-monitor/agents/azure-monitor-agent-custom-text-log-migration

Please let me know if you have any suggestions or workaround for this.

Thank you in advance.

Answer 1

Hello elukhan,

Welcome to the Microsoft Q&A and thank you for posting your questions here.

I understand that you are facing an issue on migrating from MMA to DCR table and you need to rename a column started with underscore.

Since fields starting with an underscore (_) are not allowed in DCR-based tables, you will need to rename these fields. You can use a transformation rule in your Data Collection Rule (DCR) to rename the fields during the data ingestion process. Follow the steps in the documentation - https://learn.microsoft.com/en-us/azure/azure-monitor/agents/azure-monitor-agent-custom-text-log-migration to create a DCR and define the necessary transformations to rename the fields. This is a basic example of how you might define a transformation:

    {
      "transformations": [
        {
          "sourceField": "_oldFieldName",
          "targetField": "newFieldName"
        }
      ]
    }

Then, modify your API POST command to include the new field names as defined in your DCR to make sure that the data is ingested correctly into the new table.

NOTE: Before fully migrating, test the process with a small subset of data to ensure that the transformations and data ingestion work as expected. After migration, monitor the new DCR-based table to validate that the data is being ingested correctly and that all fields are properly renamed and populated.

ADDITIONAL SUGGESTIONS YOU MIGHT LIKELY DO:

1. You should have a comprehensive mapping of all fields that need to be renamed to help in creating accurate transformation rules.
2. If you have many fields to rename, consider scripting the creation of transformation rules to automate the process.
3. Implement error handling in your API calls to catch and log any issues during the migration process.
4. Keep detailed documentation of the changes made, including the old and new field names, to assist with troubleshooting and future reference.

I hope this is helpful! Do not hesitate to let me know if you have any other questions.

---

Please don't forget to close up the thread here by upvoting and accept it as an answer if it is helpful.