Xrc Emulation; Tape Write Pipelining; Tape Read Pipelining; Device Level Acknowledgment - HP A7533A - Brocade 4Gb SAN Switch Base Administrator's Manual

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.
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