CDT: How to deploy changes from one master database to multiple databases?

Answer

Currently this is not supported.

Alternately, you would have to manually sync Target databases one by one.

For example,
If there are 3 projects running in parallel with the different Production deployment date.
Following are different master config environments & respective deployment dates to Prod:

1. Env1 – Deployment date Feb
2. Env2 – Deployment date Mar
3. Env3 – Deployment date Aug

Now any configuration which was changed/ added to Env1 should also be synced in Env2 & Env3; if not synced we will lose the changes in Env1.

For this type of situation, Once the changes have been made in Env1, you would need to sync it up with the other two environments separately.
Consequently, every time you have made a change in the 1st environment, you would need to sync the other two up manually.

To maintain the data in specific tables in the Target DB, you can explore the Append Only mode of CDT deployment. Refer the Append-Only section in Configuration Deployment Tool Guide, Section 2.3 for details.

By using this mode, all the configuration in the Target DB can be maintained while deploying the changes from the Source.