DB2 10.5 for Linux, UNIX, and Windows

XML schema for the statement-level OPTGUIDELINES element

The OPTGUIDELINES element of a statement profile defines the optimization guidelines in effect for the statement that is identified by the associated statement key. It is defined by the type optGuidelinesType.

XML Schema

   <xs:element name="OPTGUIDELINES" type="optGuidelinesType"/>
   <xs:complexType name="optGuidelinesType">
      <xs:sequence>
         <xs:group ref="general request" minOccurs="0" maxOccurs="1"/>
         <xs:choice maxOccurs="unbounded">
            <xs:group ref="rewriteRequest"/>
            <xs:group ref="accessRequest"/>
            <xs:group ref="joinRequest"/>
            <xs:group ref="mqtEnforcementRequest"/>
         </xs:choice>
     </xs:sequence>
   </xs:complexType>

Description

The optGuidelinesType group defines the set of valid sub-elements of the OPTGUIDELINES element. Each sub-element is interpreted as an optimization guideline by the DB2® optimizer. Sub-elements can be categorized as either general request elements, rewrite request elements, access request elements, or join request elements.

General request elements are used to specify general optimization guidelines, which can be used to change the optimizer's search space.
Rewrite request elements are used to specify query rewrite optimization guidelines, which can be used to affect the query transformations that are applied when the optimized statement is being determined.
Access request elements and join request elements are plan optimization guidelines, which can be used to affect access methods, join methods, and join orders that are used in the execution plan for the optimized statement.
MQT enforcement request elements specify semantically matchable materialized query tables (MQTs) whose use in access plans should be enforced regardless of cost estimates.

Note: Optimization guidelines that are specified in a statement profile take precedence over those that are specified in the global section of an optimization profile.