Glossary
C
cache
A buffer that contains frequently accessed
instructions and data; it is used to reduce access time.
Call Level Interface (CLI)
A callable API for database access, which
is an alternative to an embedded SQL API. In contrast to embedded SQL, CLI
does not require precompiling or binding by the user, but instead provides a
standard set of functions to process SQL statements and related services at
run time.
Capture program
A replication program that reads database
log or journal records to capture data about changes made to source tables.
Contrast with Apply program.
cardinality
The number of rows in a database table.
cascade rejection
The process of rejecting a replication
transaction because it is associated with a transaction that had a conflict
detected and was itself rejected.
cast function
A function used to convert instances of a
data type (origin) into instances of a different data type (target). In
general, cast functions have the name of the target data type. They have one
single argument whose type is the origin data type; their return type is the
target data type.
catalog
A set of tables and views maintained by the
database manager. These tables and views contain information such as
descriptions of tables, views, and packages.
catalog node
The node at which the catalog tables
reside. The catalog node can be a different node for each database.
CCSID
Coded character set identifier.
CDRA
Character Data Representation
Architecture.
change aggregate table
A type of target table that contains data
aggregations based on changes recorded for a source table.
change data (CD) table
A replication control table at the source
server that contains changed data for a replication source table. The Capture
program populates the CD table by copying the changes from the database log or
journal. The contents of the CD table are then copied by the Apply program to
the target table.
Character Data Representation Architecture (CDRA)
An architecture used to achieve consistent
representation, processing, and interchange of string data.
character large object (CLOB)
A sequence of characters (single-byte,
multi-byte, or both) where the length can be up to 2 gigabytes. A data type
that can be used to store large text objects. Also called character large
object string.
character string
A sequence of bytes or characters.
character string delimiter
The characters used to enclose character
strings in delimited ASCII files that are imported or exported. See delimiter.
check condition
A restricted form of search condition used
in check constraints.
check constraint
Specifies a check condition that is not
false for each row of the table on which the constraint has been defined.
check pending
A state into which a table can be put
where only limited activity is allowed on the table and constraints are not
checked when the table is updated.
circular log
A database log in which records are
overwritten if they are no longer needed by an active database. Consequently,
if a failure occurs, lost data cannot be restored during forward recovery.
Contrast with recoverable log.
CLI
Call Level Interface.
client
Any program (or workstation it is running
on) that communicates with and accesses a database server.
CLOB
Character large object.
CLP
Command Line Processor.
clustered index
An index whose sequence of key values
closely corresponds to the sequence of rows stored in a table. The degree to
which this correspondence exists is measured by statistics that are used by
the optimizer.
coded character set
A set of unambiguous rules that
establishes a character set and the one-to-one relationships between the
characters of the set and their coded representations.
coded character set identifier (CCSID)
A number that includes an encoding scheme
identifier, character set identifiers, code page identifiers, and other
information that uniquely identifies the coded graphic character
representation.
code page
A set of assignments of characters to code
points.
code point
In CDRA, a unique bit pattern that
represents a character in a code page.
code set
Encoding values for a character set that
provides the interface between the system and its input and output devices.
ISO uses code set as the term equivalent to the IBM-defined term code page.
cold start
A system start, using an initial program
load procedure. Contrast with warm start.
collating sequence
The sequence in which the characters are
ordered for the purpose of sorting, merging, comparing, and processing indexed
data sequentially.
collocated join
The result of two tables being joined in
which:
- The tables reside in a single-partition nodegroup in the same database
partition; or they are in the same partitioned nodegroup and have the same
number of partitioning columns, the columns are partition compatible, and both
tables use the same partitioning function.
- All pairs of the corresponding partitioning key columns participate in the
equijoin predicates.
column distribution value
Statistics describing the most frequent
values of some column or the quantile values. These values are used in the
optimizer to help determine the best access plan.
column function
An operation used in queries that applies
to the values from several rows. Column functions include SUM, AVG, MIN, MAX,
COUNT, STDDEV, and VARIANCE. Synonymous with aggregate function.
Command Line Processor (CLP)
A character-based interface for entering
SQL statements and database manager commands.
commit
The operation that ends a unit of work by
releasing locks so that the database changes made by that unit of work can be
perceived by other processes. This operation makes the data changes permanent.
commit point
A point in time when data is considered to
be consistent.
common critical section table
A replication control table at the source
server that is used to establish concurrency control between the Capture and
Apply programs and to prevent an update replication cycle.
Common Programming Interface Communications (CPI-C)
An API for applications that require
program-to-program communication, making use of SNA's LU 6.2 to create a
set of interprogram services.
common pruning control table
A replication control table at the source
server that coordinates the pruning of the change data and unit-of-work
control tables. The values in this table indicate how much data has been
replicated by the Apply program and can be safely pruned by the Capture
program.
common registrations table
A replication control table at the source
server that relates each source table or view to an associated change data
table and consistent change data table, if applicable.
common subscription columns table
A replication control table that contains
column details of target tables.
common subscription events table
A replication control table that defines
the events that trigger replication, including the event name and time.
common subscription set table
A replication control table that defines
the members of a subscription set including the set name, Apply qualifier,
source server, target server, and status.
common subscription statements table
A replication control table used to store
the optional SQL statements that can be run at the beginning or end of the set
subscription cycle.
common subscription targets member table
A replication control table that maps the
source and target table relationships within a subscription set.
common table expression
An expression that defines a result table
with a name (qualified SQL identifier) that can be specified as a table name
in any FROM clause in the fullselect that follows the WITH clause.
comparison operator
An infix operator used in comparison
expressions. Comparison operators are ¬< (not less than), <=
(less than or equal to), ¬= (not equal to), = (equal to), >= (greater
than or equal to), > (greater than), and ¬> (not greater than).
complete
A table attribute indicating that the
table contains a row for every primary key value of interest. As a result, a
complete source table can be used to perform a refresh of a target table.
composite key
A key composed of more than one column
from a database table.
compound SQL statement
A block of SQL statements that are
executed in a single call to the application server.
concurrency
The shared use of resources by multiple
interactive users or application processes at the same time.
condensed
A table attribute indicating that the
table contains current data rather than a history of changes to the data. A
condensed table includes no more than one row for each primary key value in
the table. As a result, a condensed table can be used to supply current
information for a refresh.
conflict detection
The process of detecting an out-of-date
row in a replica that was updated by a user application. When a conflict is
detected, the transaction that caused the conflict is rejected. See also
enhanced conflict detection, standard conflict detection.
connect
In DB2, to access objects at the database
level.
connection
(1) An association between an application
process and an application server.
(2) In data communications, an association
established between functional units for conveying information.
connection handle
Within the CLI, the data object that
contains information associated with a connection. This includes general
status information, transaction status, and diagnostic information.
consistent change data (CCD) table
A replication table that is used for
staging data, with four replication control columns. It can be one of the
following types:
- An internal CCD table that is a join of the change data table and the
unit-of-work table at the source server.
- A regular CCD table that is a copy of the internal CCD table on a remote
server.
- An external source table that is not a DB2 origin table; it is manually
updated with four replication columns and defined as a replication source
table.
consolidation replication
A replication model in which the data from
multiple source tables is replicated to a single target table. Contrast with
fan-out replication.
constraint
A rule that limits the values that can be
inserted, deleted, or updated in a table. See check constraint, referential
constraint, and unique constraint.
container
See table space container.
contention
In the database manager, a situation in
which a transaction attempts to lock a row or table that is already locked.
Control Center
A graphical interface that shows database
objects (such as databases and tables) and their relationship to each other.
From the Control Center you can perform the tasks provided by the DBA Utility,
Visual Explain, and Performance Monitor tools.
control point
(1) In APPN, a component of a node that
manages resources of that node and optionally provides services to other nodes
in the network. Examples are a system services control point (SSCP) in a type
5 node, a physical unit control point (PUCP) in a type 4 node, a network node
control point (NNCP) in a type 2.1 (T2.1) network node, and an end node
control point (ENCP) in a T2.1 end node. An SSCP and an NNCP can provide
services to other nodes.
(2) A component of a T2.1 node that manages
the resources of that node. If the T2.1 node is an APPN node, the control
point is capable of engaging in control point-to-control point sessions with
other APPN nodes. If the T2.1 node is a network node, the control point also
provides services to adjacent end nodes in the T2.1 network. See physical
unit.
control privilege
The authority to completely control an
object. This includes the authority to access, drop, or alter an object, and
the authority to extend or revoke privileges on the object to other users.
control server
The database location of the applicable
subscription definitions and apply trail table.
control table
A table in which replication source and
subscription definitions or other replication control information is stored.
conversation
In APPC, a connection between two
transaction programs over a logical unit-logical unit (LU-LU) session that
allows them to communicate with each other while processing a transaction.
conversational transaction
In APPC, two or more programs
communicating using the services of logical units (LUs).
conversation security
In APPC, a process that allows validation
of a user ID or group ID and password before establishing a connection.
conversation security profile
The set of user IDs or group IDs and
passwords that are used by APPC for conversation security.
Coordinated Universal Time (UTC)
Synonym for Greenwich Mean Time.
coordinating agent
The agent that is spawned when a request
is received by the database manager from an application. It remains associated
with the application during the life of the application. This agent
coordinates subagents that work for the application. See also subagent.
coordinator node
The node to which the application
originally connected and on which the coordinating agent resides.
coordinator subsection
The subsection of an application that
starts other subsections (if any) and returns results to the application.
copy table
See target table.
correlated reference
Reference to a column of a table that is
outside of a subquery.
correlated subquery
A subquery that contains a correlated
reference to a column of a table that is outside of the subquery.
correlation name
An identifier designating a table or view
within a single SQL statement. It can be defined in any FROM clause or in the
first clause of an UPDATE or DELETE statement.
country code
When accessing the database, the country
code of the application is used to determine the date and time presentation
(display and print) formats. It is also used with the code page to determine
the default collating sequence for the database.
CP
Control point.
CPI-C
Common Programming Interface
Communications.
CPI-C side information profile
In SNA, the profile that specifies the
conversation characteristics to use when allocating a conversation with a
remote transaction program. The profile is used by local transaction programs
that communicate through CPI Communications. It specifies the partner LU name
(the name of the connection profile that contains the remote LU name), the
mode name, and the remote transaction program name.
CP name
Control point name. A network-qualified
name of a control point consisting of a network ID qualifier identifying the
network to which the control point node belongs.
crash recovery
The process of recovering from an
immediate failure.
CS
Cursor stability.
current function path
An ordered list of schema names used in
the resolution of unqualified references to functions and data types. In
dynamic SQL, the current function path is found in the CURRENT FUNCTION PATH
special register. In static SQL, it is defined in the FUNCPATH option for PREP
and BIND commands.
cursor
A named control structure used by an
application program to point to a specific row within some ordered set of
rows. The cursor is used to retrieve rows from a set. See also unambiguous
cursor, ambiguous cursor.
cursor stability (CS)
An isolation level that locks any row
accessed by a transaction of an application while the cursor is positioned on
the row. The lock remains in effect until the next row is fetched or the
transaction is terminated. If any data is changed in a row, the lock is held
until the change is committed to the database.
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