an apparatus , program product and method utilize the retrieval status of a resource to generate an access plan for a database query that uses the resource . the retrieval status , which indicates , for example , what percentage of a given resource is already stored in working memory , and thus need not be separately retrieved during query execution , may be used to generate more accurate input / output cost estimates for access plans , and thus enable a query optimizer to better select an access plan that is optimal under given runtime conditions .