GLYPH<SM590000> SE z15 servers are provided with two 1U trusted servers inside the IBM Z server A frame:  One is always the primary SE and the other is the alternative SE. The primary SE is the  active SE. The alternative acts as the backup. Information is mirrored once per day. The  SE servers include N+1 redundant power supplies. For more information, see 10.2.3, “New Support Element” on page 415. Chapter 9. Reliability, availability, and serviceability  407