Abstract: Method to order query results, by processing a received query at least in part using a composite key index, wherein the composite key index comprises at least two key columns, wherein the at least two key columns comprise at least one pre-ordering column and an ordering column, wherein the query specifies ordering criteria to order a result set based on values of the ordering column, wherein the processing comprises receiving, from the composite key index, an ordering column value for each unique pre-ordering column value in the composite key index, identifying a first ordering column value as being ordered first according to the ordering criteria, and returning the first ordering column value as being responsive to the query.

Abstract: System, method, and computer program product to order query results, by processing a received query at least in part using a composite key index, wherein the composite key index comprises at least two key columns, wherein the at least two key columns comprise at least one pre-ordering column and an ordering column, wherein the query specifies ordering criteria to order a result set based on values of the ordering column, wherein the processing comprises receiving, from the composite key index, an ordering column value for each unique pre-ordering column value in the composite key index, identifying a first ordering column value as being ordered first according to the ordering criteria, and returning the first ordering column value as being responsive to the query.

Abstract: Method to order query results, by processing a received query at least in part using a composite key index, wherein the composite key index comprises at least two key columns, wherein the at least two key columns comprise at least one pre-ordering column and an ordering column, wherein the query specifies ordering criteria to order a result set based on values of the ordering column, wherein the processing comprises receiving, from the composite key index, an ordering column value for each unique pre-ordering column value in the composite key index, identifying a first ordering column value as being ordered first according to the ordering criteria, and returning the first ordering column value as being responsive to the query.

Abstract: System, method, and computer program product to order query results, by processing a received query at least in part using a composite key index, wherein the composite key index comprises at least two key columns, wherein the at least two key columns comprise at least one pre-ordering column and an ordering column, wherein the query specifies ordering criteria to order a result set based on values of the ordering column, wherein the processing comprises receiving, from the composite key index, an ordering column value for each unique pre-ordering column value in the composite key index, identifying a first ordering column value as being ordered first according to the ordering criteria, and returning the first ordering column value as being responsive to the query.

Abstract: In parallel process computer systems multiple tasks are simultaneously executed. However, where resource contention exists, the multiple tasks become serialized, reducing system performance. Once such resource contention is arm contention during reads for files stored under multiple arms on direct access storage devices (DASDs). According to the preferred embodiment, a method is provided that assigns read tasks in a manner that reduces the probability of arm contention during the file reads. First, the plurality of extents storing the file are correlated to their associated arm. Second, for each of the plurality of arms, the attributes of extents under that arm, preferably including the extent read times, are accumulated. Finally, the plurality of simultaneous read tasks are assigned to the plurality of extents according to the accumulated attributes such that arms that have a greater need for service are favored over arms that have a lesser need when reading the file.