HP StorageWorks 8/80 HP StorageWorks Fabric OS 6.1.x administrator guide (5697 - Page 385

XRC emulation The eXtended Remote Copy (XRC) application is a DASD application that implements disk mirroring, as supported by the disk hardware architecture and a host software component called System Data Mover (SDM). The primary volume and the secondary mirrored volume may be geographically distant across an IP WAN. The latency introduced by greater distance creates delays in anticipated responses to certain commands. The FICON pacing mechanism may interpret delays as an indication of a large data transfer that could monopolize a shared resource, and react by throttling the I/O. XRC emulation provides local responses to remote hosts, eliminating distance related delays. A FICON XRC Emulation License is required to enable XRC Emulation. Tape write pipelining FICON tape write pipelining improves performance for a variety of applications when writing to tape over extended distances. FICON tape write pipelining locally acknowledges write data records, enabling the host to generate more records while previous records are in transit across the IP WAN. If exception status is received from the device, the writing of data and emulation is terminated. The FICON Tape Emulation License is required to enable FICON tape write pipelining. Tape read pipelining FICON tape read pipelining improves performance for certain applications when reading from FICON tape over extended distances. FICON tape read pipelining reads data from tape directly from the tape device. Reading of tape continues until a threshold is reached. The buffered data is forwarded to the host in response to requests from the host. When the host sends the status accept frame indicating that the data was delivered, the read processing on the device side credits the pipeline and requests more data from the tape. If exception status is received from the device, the reading of data and emulation is terminated. The FICON Tape Emulation License is required to enable FICON tape read pipelining. Device level acknowledgment This feature generates device level acknowledgment (Acks) for non-emulated sequences when an exchange is left open until status acceptance occurs. This can reduce the time it takes to execute some non-emulated channel programs by eliminating one link round trip delay. This feature should be enabled whenever FICON Tape or FICON XRC emulation is enabled. TIN/TIR emulation This feature enhances recovery when a TIN/TIR exchange occurs as part of a channel recovery operation during tape emulation. This feature should be enabled whenever FICON Tape or FICON XRC emulation is enabled. Read block ID emulation This feature permits FICON write channel programs containing embedded read block ID commands (CCWs) with a byte count of exactly four bytes to be processed as emulated commands during write emulation processes. FTRACE concepts FTRACE is a support tool that can be used in a manner similar to that of a channel protocol analyzer. FTRACE enables troubleshooting of problems using a Telnet session rather than sending an analyzer or technical support personnel to the site. FTRACE record events that occur on the FC interface, including user defined messages and events. FTRACE includes the ability to freeze traces on certain events, and to retain the trace information for future examination. Fabric OS 6.1.x administrator guide 385