U


UCS-2

Universal Character Set, coded in 2 octets, which means that characters are represented in 16-bits per character.



UDF

See [user-defined function]
UDT

See [user-defined type]
unambiguous cursor

A cursor that allows a DBMS to determine whether blocking can be used with the answer set. A cursor that is defined FOR FETCH ONLY or FOR READ ONLY can be used with blocking, whereas a cursor that is defined FOR UPDATE cannot.



uncommitted read (UR)

An isolation level that allows an application to access uncommitted changes of other transactions. The application does not lock other applications out of the row that it is reading, unless the other application attempts to drop or alter the table.



unfenced

Pertaining to a type (characteristic) of a procedure, user-defined function, or federated wrapper that is defined to run in the database manager process. When this type of object is run (using the not fenced clause), the database manager is not protected from changes made by this object.



unfenced routine

A type of user-defined function or stored procedure that is defined to be run in the database manager process. There is no protection for the database manager from changes by this routine.



Unicode

An international character-encoding scheme that is a subset of the ISO 10646 standard. Each character supported is defined using a unique 2-byte code.



uniform resource locator (URL)

A sequence of characters that represents information resources on a computer or in a network such as the Internet. This sequence of characters includes the abbreviated name of the protocol that accesses the information resource and the information used by the protocol to locate the information resource.



union

An SQL operation that combines the results of two SELECT statements. Unions are often used to merge lists of values that are obtained from several tables.



unique constraint

The rule that no two values in a primary key or key of a unique index can be the same. Also referred to as uniqueness constraint.



unique index

An index that ensures that no identical key values are stored in a table.



unique key

A key that is constrained so that no two of its values are equal.



unit of work (UOW)

A recoverable sequence of operations within an application process. At any time, an application process is a single unit of work, but the life of an application process can involve many units of work as a result of commit or roll back operations. Synonym for transaction.



Universal Coordinated Time

The international time standard. 00:00 UTC is midnight in Greenwich, England.



untrusted clients

DB2 clients that do not have a reliable security facility such as Windows 98, Windows ME, and Classic Mac OS.



update rule

A condition enforced by the database manager that must be met before a column can be updated.



UR

See [uncommitted read (UR)]
URL

See [uniform resource locator]
user-defined function (UDF)

A database object that is created with the CREATE FUNCTION statement. All functions that are not built-in functions are user-defined functions.



user-defined type (UDT)

A data type that is not native to the database manager and was created by a user. In DB2 UDB, the term distinct type is used instead of user-defined type.



user exit program

A program written by a user that receives control at predefined user exit points. When a user exit program is invoked, the database manager passes control to the executable file. Only one user exit program can be invoked in a database manager instance.



user mapping

In a federated system, the association between the authorization ID at the federated server and the authorization ID at the data source. User mappings are needed so that distributed requests can be sent to the data source. User mappings are created when a user's authorization ID to access the federated database differs from the user's authorization ID to access a data source. Use the CREATE USER MAPPING statement to define the association and the ALTER USER MAPPING statement to modify a user mapping that you have already created.



UTC

See [Universal Coordinated Time]
UTF-8

Unicode Transformation Format, 8-bit encoding form, which is designed for ease of use with existing ASCII-based systems. The CCSID value for data in UTF-8 format is 1208.



UTF-16

Unicode Transformation Format, 16-bit encoding form, which is designed to provide code values for over a million characters and is a superset of UCS-2. The CCSID value for data in UTF-16 format is 1200.





Understanding DB2(R. Learning Visually with Examples)
Understanding DB2: Learning Visually with Examples (2nd Edition)
ISBN: 0131580183
EAN: 2147483647
Year: 2004
Pages: 313

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