I look forward to someone specific answering this one. :)
Due to the "double buffer" concept, a table is locked during the delta merge process for only a very brief time. Table writes during delta merge go to "Delta 2", which - as a delta store - is as optimized for writes in the same fashion as the 'original' Delta 1. (Reference: https://help.sap.com/saphelp_hanaplatform/helpdata/en/bd/9ac728bb57101482b2ebfe243dcd7a/content.htm)
I'm finding a lot of "experts" note that manually disabling delta merges before initial loads, completing the load, and re-enabling after the load - will increase "performance".
Perhaps I'm missing something obvious, but when people speak of performance - they're usually referring to runtime - and it's not clear why manually altering the delta merge process has any impact on runtime.
Memory - sure, I understand that the delta loads main to delta to complete, and thus there may be valid reasons for managing memory (and thus delta) manually - but not clear on why this should impact runtime performance.
To be clear, these "experts" may well know something I don't, and even I like to refer to myself as an "expert".
Or perhaps more likely - I just like to put certain terms in double quotes. ;)