Glossary
U
UDF
User-defined function.
UDT
User-defined type.
unambiguous cursor
A cursor that has been defined in a manner
that allows a relational database to determine whether blocking can be used
with the answer set. A cursor defined FOR FETCH ONLY or FOR READ ONLY can be
used with blocking, whereas a cursor defined FOR UPDATE cannot.
unbind session (UNBIND)
A request to deactivate a session between
two logical units (LUs).
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 it is reading,
unless the other application attempts to drop or alter the table.
uncoordinated transaction
A transaction that accesses more than one
resource but its commit or rollback is not being coordinated by a Transaction
Manager.
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.
unique constraint
The rule that no two values in a primary
key or key of a unique index can be the same.
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
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 rollback operations. Synonym for transaction.
unit-of-work table
A replication control table at the source
server that contains commit records read from the database log or journal. The
records include a unit-of-recovery ID that can be used to join the
unit-of-work table and the change data table to produce transaction-consistent
change data. For DB2, the unit-of-work table optionally includes the
correlation ID, which can be useful for auditing purposes.
untyped parameter marker
A parameter marker that is specified
without its target data type. It has the form of a single question mark.
update rule
A condition enforced by the database
manager that must be met before a column can be updated.
UR
Uncommitted read.
user copy table
A target table whose content matches all
or part of a source table and contains only user data columns.
user-defined distinct type
See distinct type.
user-defined function (UDF)
A function that is defined to the database
management system and can be referenced thereafter in SQL queries. It can be
one of the following functions:
- An external function, in which the body of the function is written in a
programming language whose arguments are scalar values and a scalar result is
produced for each invocation.
- A sourced function, implemented by another built-in or user-defined
function already known to the DBMS. This function can be either a scalar
function or column (aggregating) function, and returns a single value from a
set of values (for example, MAX or AVG).
user-defined performance variable
A performance variable created by a user
and added to the performance variable profile.
user-defined target table
Any type of target table that is created
by a user for an application and can be used in the replication process.
user-defined type (UDT)
A data type that is not native to the
database manager and was created by a user. See also distinct type.
user table
A table created for and used by an
application before it is defined as a replication source. It is used as the
source for updates to read-only target tables, consistent change data tables,
and replicas.
UTC
Coordinated Universal Time.
[ Top of Page | Previous Page | Next Page | Table of Contents ]
[ DB2 List of Books |
Search the DB2 Books ]