2.7.6 On/Off Capacity on Demand and CPs On/Off CoD and granular capacity On/Off CoD guidelines 2.8 Power and cooling 2.8.1 Power and cooling On/Off Capacity on Demand (CoD) provides temporary capacity for all types of characterized  PUs. Relative to granular capacity, On/Off CoD for CPs is treated similarly to the way that  CBU is handled. When temporary capacity that is requested by On/Off CoD for CPs matches the model  capacity identifier range of the permanent CP feature, the total number of active CPs equals  the sum of the number of permanent CPs plus the number of temporary CPs ordered. For  example, when a model capacity identifier 504 has two CP5s added temporarily, it becomes a  model capacity identifier 506. When the addition of temporary capacity that is requested by On/Off CoD for CPs results in a  cross-over from one capacity identifier range to another, the total number of CPs active when  the temporary CPs are activated is equal to the number of temporary CPs ordered. For  example, when a CPC with model capacity identifier 504 specifies six CP6 temporary CPs  through On/Off CoD, the result is a CPC with model capacity identifier 606. A cross-over does  not necessarily mean that the CP count for the extra temporary capacity increases. The same  504 might temporarily be upgraded to a CPC with model capacity identifier 704. In this case,  the number of CPs does not increase, but more temporary capacity is achieved. When you request temporary capacity, consider the following guidelines: For more information about temporary capacity increases, see Chapter 8, “System upgrades”  on page 315. The z14 power and cooling system is a continuation of IBM z13 with the addition of  improvements in availability, temperature tolerance, and vectored (directional) air output. The  air-cooled z14 server now has a radiator unit (RU) N+1 design for the pumps and blowers.  With the new rear cover design for vectored air output, you can choose whether the output air  goes up or down.  The water-cooled system is still an option for the z14 server. The Top Exit Power feature is  available for the z14 server. Combined with the Top Exit I/O Cabling feature, it gives you more  options when you are planning your computer room cabling. For more information about the  z14 Top Exit features, see 10.3, “Physical planning” on page 398. The system operates with two fully redundant power supplies. One is in the front side of the  Z frame, and the other is in the rear side of the Z frame. Each power supply has one or two  power cords. The number of power cords that are required depends on the system  configuration. The total loss of one power supply has no effect on system operation. GLYPH<SM590000> Temporary capacity must be greater than permanent capacity. GLYPH<SM590000> Temporary capacity cannot be more than double the purchased capacity. GLYPH<SM590000> On/Off CoD cannot decrease the number of engines on the CPC. GLYPH<SM590000> Adding more engines than are currently installed is not possible. Chapter 2. Central processor complex hardware components  77