[ic] Ancient Foundation order 'archive' function?

[DB]

Old friends: (too many to name)!

After 20+ years, my mysql/maria DB has grown to the point that while

'INSERT into transactions...'

queries complete very quickly,

UPDATE transactions/orderline transactions

are taking 6+ seconds, even when run locally.

I noticed an 'archive order' feature in the ancient Foundation back end. 
But I can't find what this does. I'd prefer to retain my order data 
going back to eternity if possible. Does anyone remember?

DB