ArcGIS, assuming you are browsing the data, doing edits, analysis and what not, needs virtually "continuous" access to the database. Each zoom or pan request will trigger SQL statements send to the database to get the latest results. You are live on the database with ArcGIS Server (ArcSDE).
If your administrator is not familiar with (ESRI) GIS and is thinking in the "old school" ETL way of accessing the geographic data (Extract-Transform-Load), where you only hit the database upon extracting some data, and putting it back in a single load process after you've done something with it, he is in for a bad day...
I think it wise if you point your administrator to relevant ESRI documentation and Help pages, to get a feel of what ArcGIS does in terms of providing connections to enterprise databases.
E.g. following pages might be a good start:
He should probably also be reading the highly recommended ESRI maintained System Design Strategies pages: