HP Surestore Disk Array 12h - And FC60 Service Manual page 271

WDTR
Write Working Set
WDTR (Wide Data Transfer Request) controls whether or not the
additional eight bits on a wide bus will be utilized in most data phases
of a SCSI command. WDTR also determines the negotiation protocol
of the host. If WDTR is enabled, (default) the disk array will initiate for
negotiation for wide transfer. If WDTR is disabled, the host will initiate
negotiation protocol. In either case, the disk will always respond to any
requests made by the host.
The Write Working Set is the number of unique data blocks written to
the disk array over a period of time. To maintain performance, the write
working set should not consistently exceed the amount of RAID 0/1
space available.
Glossary
271