Glossary
R
RDBMS
Relational database management system.
read stability (RS)
An isolation level that locks only those
rows that an application retrieves within a transaction. It ensures that any
qualifying row read during a transaction is not changed by other application
processes until the transaction is completed, and that any row changed by
another application process is not read until the change is committed by that
process. Read stability allows more concurrency than repeatable read, and less
than cursor stability.
rebind
To create a new package for an application
program that was previously bound. For example, if an index is added for a
table accessed by a program, the package must be rebound for it to take
advantage of the new index.
record
The storage representation of a single row
of a table.
recording
The information from performance snapshots
that can be viewed at a later time.
recoverable log
A database log in which all log records
are retained so that, in the event of a failure, lost data can be recovered
during forward recovery. Contrast with circular log.
recovery
(1) The act of resetting a system, or data
that is stored in a system, to an operable state following damage.
(2) The process of rebuilding databases by
restoring a backup and rolling forward the logs associated with it.
recovery log
See database log.
recovery pending
A state of the database or table space. A
database or table space is put in recovery pending state when it is restored
from a backup. While the database or table space is in this state, its data
cannot be accessed.
recursion cycle
The cycle that occurs when a fullselect
within a common table expression includes the name of the common table
expression in a FROM clause.
recursive common table expression
A common table expression that refers to
itself in a FROM clause from the fullselect. Recursive common table
expressions are used to write recursive queries.
recursive query
A fullselect that uses a recursive common
table expression.
referential constraint
The referential integrity rule that the
nonnull values of the foreign key are valid only if they also appear as values
of a parent key.
referential integrity
The state of a database in which all
values of all foreign keys are valid.
refresh
A process in which all of the data of
interest in a user table is copied to the target table, replacing existing
data.
regular table space
A table space that can store any
nontemporary data.
rejected transaction
A transaction containing one or more
updates from replica tables that are out of date in comparison to the origin
table.
relational database
A database that can be perceived as a set
of tables and manipulated in accordance with the relational model of data.
remote database
A database that is physically located on a
workstation other than the one in use. Contrast with local database.
remote unit of work (RUOW)
A unit of work that allows for the remote
preparation and execution of SQL statements.
repeatable read (RR)
An isolation level that locks all the rows
in an application that are referenced within a transaction. When a program
uses repeatable read protection, rows referenced by the program cannot be
changed by other programs until the program ends the current transaction.
replica
A type of target table that can be updated
locally and receives updates from a user table through a subscription
definition. It can be a source for updating the user table or read-only target
tables.
replication
The process of taking changes that are
stored in the database log or journal at the source server and applying them
to the target server.
replication administrator
The user responsible for defining
replication sources and subscriptions. This user can also run the Capture and
Apply programs.
replication source
A database table that is defined as a
source for replication. This type of table can accept copy requests and is the
source table in a replication subscription set. See also subscription set.
replication subscription
A specification for copying changed data
from replication sources to target tables at a specified time and frequency,
with the option of enhancing data. It defines all of the information that is
required by the Apply program to copy data.
reserved word
(1) In programming languages, a keyword that
may not be used as an identifier. (I)
(2) A word used in a source program to
describe an action to be taken by the program or compiler. It must not appear
in the program as a user-defined name or a system name.
(3) A word that has been set aside for special
use in the SQL standard.
restore
To return a backup copy to the active
storage location for use.
restore set
A backup copy of a database or table space
plus zero or more log files that, when restored and rolled forward, bring the
database or table space back to a consistent state.
result set
Synonym for result table.
result table
The set of rows produced by the evaluation
of a SELECT statement. Synonymous with result set.
revoke
To remove a privilege or authority from an
authorization ID.
RID (Record ID)
A number that is used internally by DB2 to
uniquely identify a record in a table. It contains enough information to
address the page in which the record is stored.
rollback
The process of restoring data changed by
SQL statements to the state at its last commit point. See also point of
consistency.
roll-forward
The process of updating the data in a
restored database by applying changes recorded in the database log. See
forward recovery.
row
The horizontal component of a table
consisting of a sequence of values, one for each column of the table.
RR
Repeatable read.
RS
Read stability.
RUOW
Remote unit of work.
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