GLYPH<SM590000> Air-cooled system, which features fans with N+1 redundancy and a new designed  front-to-rear cooling system. GLYPH<SM590000> Redundant 1 Gbps Ethernet service network with virtual LAN (VLAN). GLYPH<SM590000> The PCIe+ I/O drawer is available for z14 ZR1. It and all of the PCIe I/O drawer-supported  adapters can be installed concurrently. GLYPH<SM590000> Memory interface logic to maintain channel synchronization when one channel goes into  replay. z14 ZR1 can isolate recovery to only the failing channel. GLYPH<SM590000> PCIe redrive hub cards plug straight in (no blind mating of connector). Simplified plugging  that is more reliable is included. GLYPH<SM590000> ICA (short distance) coupling cards plug straight in (no blind mating of connector).  Simplified plugging that is more reliable is included. GLYPH<SM590000> Coupling Express LR (CE LR) coupling cards plug into the PCIe I/O Drawer, which allows  more connections with the same bandwidth. GLYPH<SM590000> Continued focus on firmware quality The service network in the system gives the machine code the capability to monitor each  internal function in the system. This process helps to identify problems, maintain the  redundancy, and concurrently replace a part. Through the implementation of the VLAN to  the redundant internal Ethernet service network, these advantages are improved, which  makes the service network easier to handle and more flexible. An  unscheduled outage  occurs because of an unrecoverable malfunction in a hardware  component of the system.  The following improvements can minimize unscheduled outages: For LIC and hardware design, failures are eliminated through rigorous design rules;  design walk-through; peer reviews; element, subsystem, and system simulation; and  extensive engineering and manufacturing testing. RAIM on IBM Z systems is a concept similar to the concept of Redundant Array of  Independent Disks (RAID). The RAIM design detects and recovers from dynamic random  access memory (DRAM), socket, memory channel, or DIMM failures. The RAIM design  requires the adding one memory channel that is dedicated for RAS.  The parity of the four data DIMMs is stored in the DIMMs that are attached to the fifth  memory channel. Any failure in a memory component can be detected and corrected  dynamically. z14 ZR1 inherited this memory architecture. The memory system on z14 ZR1 is implemented with an enhanced version of the  Reed-Solomon ECC that is known as 90B/64B. It provides protection against memory  channel and DIMM failures.  A precise marking of faulty chips helps ensure timely DIMM replacements. The design of  the z14 ZR1 further improved this chip marking technology. Graduated DRAM marking is  available, and channel marking and scrubbing calls for replacement on the third DRAM  failure is available. For more information about the memory system on z14 ZR1, see 2.5,  “Memory” on page 38. 9.7.2 Unscheduled outages GLYPH<SM590000> Memory subsystem improvements Chapter 9. Reliability, availability, and serviceability  337