User Manual

SCSI Commands Reference Manual, Rev. J 32
www.seagate.com Definitions, Symbols, Abbreviations, Keywords, And Conventions
Unit attention condition
A state that a logical unit maintains while it has asynchronous status information to report to the initiator ports associated with one or more I_T
nexuses. See SAM-5.
Universal time (UT)
The time at longitude zero, colloquially known as Greenwich Mean Time. See http://aa.usno.navy.mil/fa
q/docs/UT.html.
URI Schemes
The Internet Assigned Numbers Authority maintains a list of schemes for URI and URL names at http://www.iana.or
g/assignments/uri-schemes.
User data
Data contained in logical blocks that is not protection information.
UTF-8
A character set that is a transformation format of the character set defined by ISO 10646. See RFC 2279.
Vendor specific (VS)
Something (e.g., a bit, field, or code value) that is not defined by SPC-5 and may be vendor defined.
Volatile cache memory or Volatile cache
Cache memory that does not retain data through power cycles.
Volatile medium
Medium that does not retain data written to it for a subsequent read operation through power cycles (e.g., a silicon memory device that loses
data written to it if device power is lost).
Well known logical unit
A logical unit that only does specific functions. Well known logical units allow an application client to issue requests to receive and manage
specific information usually relating to a SCSI target device.
Well known logical unit number (W-LUN)
The logical unit number that identifies a well known logical unit.
XOR operation
Performing an XOR bitwise on two identical-sized multiple-bit input values (e.g., the current value of a logical block and the new value for that
logical block). In a storage array implementing a redundancy group, the XOR operation is used in error correction algorithms and may be per-
formed by the storage array controller or by the direct-access block devices.
XOR-protected data
Logical blocks, including user data and protection information, if any, that are part of a redundancy group.
Zero
The logical false condition of a variable.
Zero-padded
A type of field in which unused bytes are placed at the end of the field (i.e., highest offset) and are filled with zeros.