5 Central processor complex  channel subsystem This chapter describes the concepts of the z15 channel subsystem, including multiple  channel subsystems and multiple subchannel sets. It also describes the technology,  terminology, and implementation aspects of the channel subsystem. This chapter includes the following topics: GLYPH<SM590000> 5.1, “Channel subsystem” on page 206 GLYPH<SM590000> 5.2, “I/O configuration management” on page 214 GLYPH<SM590000> 5.3, “Channel subsystem summary” on page 215 ' Copyright IBM Corp. 2 020. All rights reserved. 205