Oracle began laying off up to 30,000 employees globally, notifying them via a 6 a.m. email from "Oracle Leadership" with no prior warning from HR or managers.

It was not a phone call. It was not a meeting. For thousands of Oracle employees across the globe, Tuesday morning began with a single email landing in their inboxes just after 6 a.m. EST — and by the time they finished reading it, their careers at one of the world’s largest technology companies were over.

Oracle has launched what analysts believe could be the most extensive layoff in the company’s history, with estimates suggesting the cuts will affect between 20,000 and 30,000 employees — roughly 18% of its global workforce of approximately 162,000 people. Workers in the United States, India, and other regions all reported receiving the same termination notice at nearly the same hour, sent under the name “Oracle Leadership.”