Some queries can gain a performance advantage when the result set from the query does not use an index to order the results. In older versions of the DataServer for Microsoft SQL Server, results sets were always indexed because queries and their results were gathered in segments with new cursors being generated for each query segment. However, most advanced drivers and data sources now allow a single cursor to be retained for the life of a given query, even across a transaction boundary. Drivers that can preserve cursors are allowed to execute unindexed queries if the PRGRS_ALWAYS_INDEX option is set to 0 (off). When this option is off and the user does not specify an index or BY clause for the results of their ABL statement and the particular ABL being executed does not require scrolling capability in the OpenEdge client, the query result will remain unindexed by the DataServer.

Note: In an unindexed query, the DataServer will not send an ORDER BY clause to the data source. However, the DataServer has no control over whether or not the actual data source utilizes an index in order to generate a result set.