Read Diagnostic Parameter Extended Link Service support N_Port ID Virtualization enhancement Export/import physical port WWPNs for FCP Channels FICON support for multiple-hop cascaded SAN configurations To improve the accuracy of identifying a failed component without unnecessarily replacing  components in a SAN fabric, a new Extended Link Service (ELS) command called Read  Diagnostic Parameters (RDP) was added to the Fibre Channel T11 standard to allow Z  servers to obtain extra diagnostic data from the SFP optics that are throughout the SAN  fabric.  z15, z14 ZR1, z14 M0x, z13s, and z13 servers now can read this extra diagnostic data for all  the ports that are accessed in the I/O configuration and make the data available to an LPAR.  For z/OS LPARs that use FICON channels, z/OS displays the data with a new message and  display command. For Linux on Z, z/VM, and z/VSE, and LPARs that use FCP channels, this  diagnostic data is available in a new window in the SAN Explorer tool. N_Port ID Virtualization (NPIV) allows multiple system images (in LPARs or z/VM guests) to  use a single FCP channel as though each were the sole user of the channel. First introduced  with IBM z9fi EC, this feature can be used with earlier FICON features that were carried  forward from earlier servers. By using the FICON Express16S (or newer) as an FCP channel with NPIV enabled, the  maximum numbers of the following aspects for one FCP physical channel are doubled: For more information about operating systems that support NPIV, see “N_Port ID  Virtualization” on page 303 . IBM Z automatically assigns worldwide port names (WWPNs) to the physical ports of an FCP  channel that is based on the PCHID. This WWPN assignment changes when an FCP channel  is moved to a different physical slot position.  z15, z14 ZR1, z14 M0x, z13, and z13s servers allow for the modification of these default  assignments, which also allows FCP channels to keep previously assigned WWPNs, even  after being moved to a different slot position. This capability can eliminate the need for  reconfiguration of the SAN in many situations, and is especially helpful during a system  upgrade (FC 0099 - WWPN Persistence). Note:  For more information about the FICON enhancement, see  Get More Out of Your IT  Infrastructure with IBM z13 I/O Enhancements , REDP-5134. Before the introduction of z13 and z13s servers, IBM Z FICON SAN configurations supported  a single ISL (a single hop) in a cascaded FICON SAN environment only. The z15, z14 ZR1,  z14 M0x, z13, and z13s servers now support up to three hops in a cascaded FICON SAN  environment. This support allows clients to more easily configure a three- or four-site disaster  recovery solution.  For more information about the FICON multi-hop, see the FICON Multihop: Requirements  and Configurations white paper at the IBM Techdocs Library website. 178  IBM z15 (8561) Technical Guide GLYPH<SM590000> Maximum number of NPIV hosts defined: 64 GLYPH<SM590000> Maximum number of remote N_Ports communicated: 1024 GLYPH<SM590000> Maximum number of addressable LUNs: 8192 GLYPH<SM590000> Concurrent I/O operations: 1528