At once and As a whole

At once adverb - Without delay or hesitation; with no time intervening.

As a whole and at once are semantically related in at the same time topic. In some cases you can use "As a whole" instead an adverb phrase "At once".

At once and as a whole are semantically related in at the same time topic. Sometimes you can use "At once" instead an adverb phrase "As a whole".