Best practices for Migrting CMDB data from one class to a new custom class?

[ashwanikumar]

Hi Team,

My customer has a legacy implementation where computer records were created under an incorrect CMDB class. As a result, ServiceNow is classifying them as servers (1:1), leading to additional licensing charges.

We need to migrate these records from the custom/incorrect class to the appropriate class. The table contains over 20 million records, so we are looking for the most efficient and scalable approach.

What are the recommended best practices for migrating large volumes of CI data from one class to another in ServiceNow?

Thanks,

Kumar

[Fabian Kunzke]

Hey,

So first of all - and whenever the docs load again - get yourself familiar with the following docs entry: https://www.servicenow.com/docs/r/servicenow-platform/configuration-management-database-cmdb/t_Manua...

For manual reclassification you will need to understand 3 concepts:

1) Moving to a higher class (downgrade) [server -> computer]

2) Moving to a lower class (upgrade) [server -> windows server]

3) Moving horizontally [server -> router]

All of these are possible by just changing the "sys_class_name" field of each record to the desired class. However, there are some issues with just moving stuff. For the case 1) and 3) you will need to make sure that all the fields of the CI records are in the target class. Otherwise you will loose the data.

Lastly, this job will run for a long time. So here are just some tips to make sure you are ready for issues:

1) Back up the instance before you do

2) Ideally schedule the job whenever your customer is off [e.g. weekends]

3) Make sure the script updates the records in batches or individually. Be prepared for it failing and you having to run it again

That's it. Usually nothing goes wrong when you prepare it well.

Regards
Fabian

[Mark Manders]

Are they just there and do you need to reclassify them, or do you have integrations/discovery running that updates them? IRE could help you, depending on how everything is maintained.

[Pratiksha]

How is the data currently being populated in the CMDB—manually or via SGC?

If the data is populated manually, the migration should be done in controlled chunks to minimize risk. As discussed, while the data is currently loaded under the Server class, the correct target class should be Computer. Both classes share many common attributes, which makes this transition feasible with proper planning.

The recommended approach is:

1. Class mapping – identify the correct target class (Computer)

2. Attribute mapping – ensure all required and critical attributes are mapped correctly

3. Data movement – migrate the records in phases

Please note that moving data from Server to Computer is considered a class downgrade, and this should be handled carefully. The primary objective should be to preserve all relationships, historical data, and operational integrity during the transition.

Regards,

Pratiksha