This function merges the full, differential, and incremental delta files on your storage into a single full file. The advantage of using this function is it will speed up the restore of files and save some space on the storage. As a single (merged) full file can be restored faster than a file consisting of full plus related incremental files, which will require a lengthy merging process after restoring to a client machine.
Delta merge applies to full, differential, and incremental delta files which reside in the data area only. The criteria for file merging is governed by the retention policy setting for the backup set.
The delta merge of differential delta with the full file, will only apply if there are incremental delta files present in the delta chain.