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).