2.1 Channel subsystem (CSS)2.1.1 Multiple channel subsystems2.1.2 Maximum 10 logical partitions in CSS52.1.3 Multiple image facility (MIF)2.2 Logical partitions (LPARs)2.3 Subchannel sets2.4 Channels2.4.1 Physical Channel ID (PCHID)2.4.2 Channel Path ID (CHPID)2.4.3 Control unit (CU)2.4.4 I/O device2.4.5 Adapter ID (AID)2.4.6 Channel path sharing2.4.7 Channel program2.4.8 System assist processor (SAP)2.4.9 Hardware system area (HSA)2.5 Defining multiple CSSs and the fourth subchannel set2.6 Channel activation2.6.1 Activation processes2.7 CPC drawer: Fanout cards and adapters2.7.1 I/O drawer and PCIe I/O drawer2.7.2 I/O drawer domains, slots and PCHIDs2.7.3 PCIe drawer domains, slots, and PCHIDs