Progress
DataServer for
Microsoft SQL Server
Guide
Query Tuning with Connection and Startup Parameters
You can control aspects of DataServer query handling not only programmatically within 4GL statements, but also through startup and connection parameter options as described in this section.
NOTE: Startup and connection parameters override query-tuning defaults. However, options set in the QUERY–TUNING phrase take precedence over startup and connection parameters. For example, if you specify NO–DEBUG for a query within your application, specifying qt_debug,SQL at connection time overrides the default application behavior but does not override the NO–DEBUG option that you specified for the query. See the "Query Tuning" section in "Programming Considerations," for more information.You override query-tuning defaults with the DataServer (-Dsrv) connection parameter when you connect to a SQL Server database. The syntax is:
An alternate syntax for the -Dsrv parameter is as follows:
Table 4–2 describes the query-tuning options that you can specify with the -Dsrv parameter. Unless otherwise indicated, these options apply at both compile time and run time. See Table 4–2, “Query-tuning Options” for more details.
Table 4–2: Connection Query-tuning Options Option Description qt_no_debugqt_debug,SQLqt_debug,EXTENDEDqt_debug,CURSORqt_debug,PERFORMANCEqt_debug,CALL_SUMMARYqt_debug,VERBOSE
Specifies whether the DataServer prints debugging information that it generates for the query to thedataserv.lg
file. The default is qt_no_debug, to supply no debugging information. To override the default, specify qt_debug,option as follows:
- Specify qt_debug,SQL to print the SQL statements that the DataServer executes.
- Specify qt_debug,EXTENDED to print information such as cursor statistics in addition to the SQL statements executed by the DataServer.
- Specify qt_debug,CURSOR to print information about the cursors that the DataServer uses for internal calls and for opening queries.
- Specify qt_debug,PERFORMANCE to print information on the amount of time that certain operations take.
- Specify qt_debug,CALL_SUMMARY to print information on cursors and timing.
- Specify qt_debug,VERBOSE to print all of the information gathered by the other qt_debug options.
For more detailed descriptions of these options, see Table 4–3. qt_lookaheadqt_no_lookahead Specifies whether the DataServer uses lookahead or standard cursors. The default with statements that use NO-LOCK is qt_lookahead.Specify qt_no_lookahead for behavior that is consistent with Progress. qt_separate_connectionqt_no_separate_connection Specifies whether each cursor should use a separate connection to the SQL Server™ database. The default is qt_no_separate_connection, which provides behavior that is consistent with Progress.Specify qt_separate_connection to use a separate connection. Executing cursors in separate connections can improve performance because the DataServer does not have to restart the cursors. qt_cache_size,integer Specifies the size in bytes of the cache used by lookahead cursors. A larger cache size can improve performance for queries that return a large number of records because the DataServer might need fewer SQL statements to get the results.Minimum: The DataServer always caches at least one record.Maximum: NoneDefault: 30000
The following example shows how to use the query-tuning options to enhance performance. The DataServer opens a separate connection to MSS (Microsoft® SQL Server™) for each cursor and writes an extended report on the SQL statements it executes:
Progress provides a startup parameter called Server Join (-nojoinbysqldb) that controls the default JOIN–BY–SQLDB behavior. You specify this parameter in the startup command for your Progress session. It overrides the JOIN–BY–SQLDB default so that the client evaluates and performs joins. Using this parameter might slow performance, but it provides results that are consistent with Progress behavior. See "Programming Considerations," for more information.
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