Databases for Harmony DCU . What is the difference between a .ALD file and a .ADD file?
An ALD-file is a backup/dump of the online DCU database which you generate via "file operations".
An ADD-file on the other hand is generated when you create a database in CTK using "database builder". It is in fact an offline database, meaning that if you change something on the ADD database, it will not be changed in the DCU, while changes made via "DCU-resident configuration" -> "DB" will affect the online configuration.
However making changes via the database builder isn't that functional since it's only offline and for a change to be implemented in the DCU you will need to upload the ADD which will make the DCU go offline while uploading.
The online DCU configuration on the other hand will make the changes immediately. -> This way is safer since you configure everything step by step and see the effects online in an instance, while using the offline database and uploading the file will leave you with an unknown number of possible errors since the changes in the database where not tested online one by one.
For these reasons I recommend only using the online DCU configuration and the ALD files.