Also, the changes to the architectures provide end-to-end system enhancements to improve  reliability, availability, and serviceability (RAS). zHPF is compatible with the following standards: For example, the zHPF channel programs can be used by the z/OS OLTP I/O workloads,  Db2, VSAM, the partitioned data set extended (PDSE), and the z/OS file system (zFS). At the zHPF announcement, zHPF supported the transfer of small blocks of fixed size data  (4 K) from a single track. This capability was extended, first to 64 KB, and then to multitrack  operations. The 64 KB data transfer limit on multitrack operations was removed by z196. This  improvement allows the channel to fully use the bandwidth of FICON channels, which results  in higher throughputs and lower response times. The multitrack operations extension applies exclusively to the FICON Express16S+, FICON  Express16S, and FICON Express8S, on the z14 M0x, z14 ZR1, z13, z13s, zEC12, and  zBC12, when configured as CHPID type FC and connecting to z/OS. zHPF requires matching  support by the DS8000 series. Otherwise, the extended multitrack support is transparent to  the control unit. zHPF is enhanced to allow all large write operations (greater than 64 KB) at distances up to  100 kilometers (62.13 miles) to be run in a single round trip to the control unit. This process  does not increase the I/O service time for these write operations at extended distances. This  enhancement to zHPF removes a key inhibitor for clients that are adopting zHPF over  extended distances, especially when the IBM HyperSwap capability of z/OS is used. From the z/OS perspective, the FICON architecture is known as  command mode  and the  zHPF architecture is known as  transport mode . During link initialization, the channel node and  the control unit node indicate whether they support zHPF. Requirement:  All FICON channel path identifiers (CHPIDs) that are defined to the same  LCU must support zHPF. The inclusion of any non-compliant zHPF features in the path  group causes the entire path group to support command mode only. GLYPH<SM590000> Fibre Channel Framing and Signaling standard (FC-FS) GLYPH<SM590000> Fibre Channel Switch Fabric and Switch Control Requirements (FC-SW) GLYPH<SM590000> Fibre Channel Single-Byte-4 (FC-SB-4) standards The mode that is used for an I/O operation depends on the control unit that supports zHPF  and its settings in the z/OS operating system. For z/OS use, a parameter is available in the  IECIOSxx member of SYS1.PARMLIB ( ZHPF=YES  or  NO ) and in the  SETIOS  system command to  control whether zHPF is enabled or disabled. The default is  ZHPF=NO .  Support is also added for the  D IOS,ZHPF  system command to indicate whether zHPF is  enabled, disabled, or not supported on the server. Similar to the existing FICON channel architecture, the application or access method provides  the channel program (CCWs). How zHPF (transport mode) manages channel program  operations is different from the CCW operation for the existing FICON architecture (command  mode).  While in command mode, each CCW is sent to the control unit for execution. In transport  mode, multiple channel commands are packaged together and sent over the link to the  control unit in a single control block. Fewer processors are used compared to the existing  FICON architecture. Certain complex CCW chains are not supported by zHPF. 246  IBM 14 Model ZR1 Technical Guide