Clustering
Over time, updates might cause rows on data pages to change
location lowering the degree of clustering that exists
between an index and the data pages.
Container
A container is a physical storage location
of the data.
Cost Cost, in the context of access plans access
plans, is the estimated total resource usage necessary to execute
the access plan for a statement (or the elements of a statement).
Cursor blocking Cursor blocking is a technique that reduces
overhead by having the database manager retrieve a block of
rows in a single operation.
Database-managed table space
There are two types of table spaces that can
exist in a database: database-managed space (DMS), and system-managed
space (SMS).
Dynamic SQL or XQuery Dynamic SQL or XQuery statements are statements
that are prepared and executed within an application program while
the program is running.
Explain snapshot
With Visual Explain, you can examine the contents of an
explain snapshot. An explain snapshot is compressed information
that is collected when an SQL statement is explained.
Explainable statement
An explainable statement is an SQL or XQuery
statement for which an explain operation can be performed.
Explained statement
An explained statement is an SQL or XQuery
statement for which an explain operation has been performed.
Operand
An operand is an entity on which an operation is performed.
Operator
An operator is either an action that must
be performed on data, or the output from a table or an index, when
the access plan for an SQL or XQuery statement is executed.
Optimizer
The optimizer is the component of the SQL
compiler that chooses an access plan for a data manipulation language
(DML) SQL statement.
Package
A package is an object stored in the database
that includes the information needed to process the SQL statements
associated with one source file of an application program.
Predicate
A predicate is an element of a search condition
that expresses or implies a comparison operation. Predicates are included
in clauses beginning with WHERE or HAVING.
Query optimization class
A query optimization class is a set of query
rewrite rules and optimization techniques for compiling queries.
Selectivity of predicates Selectivity refers to the probability that
any row will satisfy a predicate (that is, be true).
Star join
A set of joins are considered to be a star join when a
fact table (large central table) is joined to two or more dimension
tables (smaller tables containing descriptions of the column values
in the fact table).
Static SQL or XQuery
A static SQL or XQuery statement is embedded
within an application program. All these embedded statements must
be precompiled and bound into a package before the application
can be executed.
System-managed table spaces
There are two types of table spaces that can exist in a
database: system-managed space (SMS) and database-managed
space (DMS).
Table spaces
It is easier to manage very large databases if you partition
them into separately managed parts called table spaces.
A table space lets you assign the location of data to particular logical
devices or portions thereof.
Visual Explain
Visual Explain lets you view the access plan for explained
SQL or XQuery statements as a graph. You can use the information available
from the graph to tune your queries for better performance.
DB2 Version 9.7 for Linux, UNIX, and Windows