Dear SAP FI Experts,
Can I add an alternative account number in master data of a G/L account after postings have been made to this account, without having to reverse all the posting?

Background: We have a G/L account in our system where was already posted to.
What is the impact if I try to add an alternate account number to this G/L account at database level with an ABAP report?
Thanks in advance for the info.
With kind regards
Emal