Figure 2-37 Rear door heat exchanger plumbing schematic Table 2-14 System structure summary 2.10 Summary Figure 2-37 shows an example of various frame configurations. Every frame includes a heat  exchanger when the water-cooling feature is ordered.  If one client water supply or one WCU fails, the remaining feed maintains PU SCM cooling for  the frame. The WCUs and the associated drive card are concurrently replaceable. In addition,  the heat exchangers can be disconnected and removed from the system concurrently. All aspects of the z15 structure are listed in Table 2-14 86  IBM z15 (8561) Technical Guide Description Max34 Max71 Max108 Max145 Max190 Maximum number  of characterized  PUs 34 71 108 145 190 Number of CPs 0 - 34 0 - 71 0 - 108 0 - 145 0 - 190 Number of IFLs 0 - 34 0 - 71 0 - 108 0 - 145 0 - 190 Number of  Unassigned IFLs 0 - 33 0 - 70 0 - 107 0 - 144 0 - 189 Number of ICFs 0 - 34 0 - 71 0 - 108 0 - 145 0 - 190 Number of zIIPs 0 - 22 0 - 46 0 - 70 0 - 96 0 - 126 Standard SAPs 4 8 12 16 22 Additional SAPs 0 - 8 0 - 8 0 - 8 0 - 8 0 - 8