DCFM Professional Plus User Manual (53-1001774-01, June 2010)

418 DCFM Professional Plus User Manual
53-1001774-01
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FICON emulation features
FICON emulation supports FICON traffic over IP WANs using FCIP as the underlying protocol. FICON
emulation features support performance enhancements for specific applications. If you are using
FCIP for distance extension in a FICON environment, evaluate the need for these features before
you run the FCIP configuration wizard. FICON emulation may be configured by selecting Advanced
Settings on the Add Tunnel or Edit Tunnel dialogs. The following features are available:
• XRC emulation.
• Tape write pipelining.
• Tape read pipelining.
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.