DB2 10.5 for Linux, UNIX, and Windows
Explain concepts
This section contains Explain conceptual information.
Access plan
Certain data is necessary to resolve an
explainable statement
. An
access plan
specifies an order of operations for accessing this data.
Cursor blocking
Cursor blocking
is a technique that reduces overhead by having the database manager retrieve a
block
of rows in a single operation.
Explain information for data operators
Explain snapshot
An
explain snapshot
is compressed information that is collected when an SQL statement is explained.
Sample XML document fragment for Explain XML operators
This sample XML document fragment is used in the discussion of the Explain XML operators XSCAN, XISCAN, and XANDOR.
Selectivity of predicates
Selectivity
refers to the probability that any row will satisfy a predicate (that is, be true).
DB2 10.5 for Linux, UNIX, and Windows
DB2 10.5 for Linux, UNIX, and Windows