So short answer is you can either export the de and then import it into All Subscribers (Automated or manual) or utilize WSProxy to pull directly from the DE and push the returned data into Subscribers.
Long answer is below:
For the extract:
Pros
- It is simple and requires no technical knowledge
- It can be easily automated in Automation Studio
- It is usually a more efficient method when dealing with a large audience
- Has no time out limit.
Cons
- It requires filter interactions and selecting those filtered DEs to only pull specific results
- It involves multiple steps and set ups. Increasing risk of human error
- It is reliant on SFTP and location set up knowledge and permissions.
- Requires decent up front work to correctly set up
For WSProxy
Pros
- It is versatile and easy to filter out what you need (records, columns, etc.)
- It is fully customizable as it would be handled via a script and not a defined process.
- As it is pulling via WSProxy it is fast and performant
Cons
- It requires technical knowledge of SSJS, WSProxy and SOAP API.
- As it is a script activity, it has a 30 minute timeout window. Would need to add in process to account for this.
- Requires pagination as it has a max payload of 2000 records.
Here is an article I wrote on this exact issue that may help give more context.
I would use Extract if you are looking to pull the full file and upsert it each time (and it is hundreds of thousands of records or more).
I would use WSProxy if it is low volume or if you need high customization on filtering who should be included or not in the export/import or if you only want certain fields added/updated.
