The following sections describe the steps that are used if dual AC power is lost to the entire  frame. When an on-battery condition shutdown begins, the following events occur: When power is restored, the DS8880 needs to be powered on manually, unless the remote  power control mode is set to  automatic .  Note:  Be careful before you decide to set the remote power control mode to  automatic . If  the remote power control mode is set to  automatic , after input power is lost, the DS8880 is  powered on automatically as soon as external power becomes available again. For more  information about how to set power control on the DS8880, see the IBM Knowledge Center  at the following website: https://www.ibm.com/support/knowledgecenter/ST5GLJ/ds8000_kcwelcome.html After the DS8880 is powered on, the following events occur: Chapter 3. Reliability, availability, and serviceability on the IBM DS8880  83 As shown in Figure 3-1 on page 78, each CPC on a DS8886 is connected to all four I/O  enclosures (base frame) or all eight I/O enclosures when the first expansion frame is  installed, by PCI Express cables. This configuration makes each I/O enclosure an extension  of each processor complex. The DS8884 has a base of two I/O enclosures, and a maximum  of four. For more information, see 2.3.5, “Peripheral Component Interconnect Express adapters” on  page 47.  The DS8880 connectivity between the CPC and the I/O enclosures uses the many strengths  of the PCIe architecture.  1. All host adapter I/O is blocked. 2. Each CPC begins copying its NVS data to internal disk (not the storage drives). For each  CPC, two copies are made of the NVS data. This process is referred to as fire hose dump  (FHD). 3. When the copy process is complete, each CPC shuts down. 4. When the shutdown in each CPC is complete, the DS8880 is powered off. 1. When the CPCs power on, the PHYP loads and power-on self-test (POST) runs. 2. Each CPC begins the initial microcode load (IML). 3. At an early stage in the IML process, the CPC detects NVS data on its internal disks and  restores the data to destage it to the storage drives. 3.3.1 I/O enclosures 3.3 Data flow in the DS8880 Power restored Power loss