Access requests

The accessRequest group defines the set of valid access request elements. An access request specifies an access method for a table reference.

XML Schema

   <xs:group name="accessRequest">
      <xs:choice>
         <xs:element name="TBSCAN" type="tableScanType"/>
         <xs:element name="IXSCAN" type="indexScanType"/>
         <xs:element name="LPREFETCH" type="listPrefetchType"/>
         <xs:element name="IXAND" type="indexAndingType"/>
         <xs:element name="IXOR" type="indexOringType"/>
         <xs:element name="XISCAN" type="indexScanType"/> 
         <xs:element name="XANDOR" type="XANDORType"/>
         <xs:element name="ACCESS" type="anyAccessType"/>
      </xs:choice>
   </xs:group>

Description

• TBSCAN, IXSCAN, LPREFETCH, IXAND, IXOR, XISCAN, and XANDOR

  These elements correspond to Db2® data access methods, and can only be applied to local tables that are referenced in a statement. They cannot refer to nicknames (remote tables) or derived tables (the result of a subselect).

• ACCESS

  This element, which causes the optimizer to choose the access method, can be used when the join order (not the access method) is of primary concern. The ACCESS element must be used when the target table reference is a derived table. For XML queries, this element can also be used with attribute TYPE = XMLINDEX to specify that the optimizer is to choose XML index access plans.