<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html lang="en-us" xml:lang="en-us"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <meta name="security" content="public" /> <meta name="Robots" content="index,follow" /> <meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' /> <meta name="DC.Type" content="reference" /> <meta name="DC.Title" content="Connection string keywords - Performance properties" /> <meta name="abstract" content="Use these iSeries Access ODBC driver connection string keywords to change Performance properties of the ODBC connection." /> <meta name="description" content="Use these iSeries Access ODBC driver connection string keywords to change Performance properties of the ODBC connection." /> <meta name="DC.Relation" scheme="URI" content="connectkeywords.htm" /> <meta name="DC.Relation" scheme="URI" content="odbcfinetunercdblock.htm" /> <meta name="copyright" content="(C) Copyright IBM Corporation 1999, 2006" /> <meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 1999, 2006" /> <meta name="DC.Format" content="XHTML" /> <meta name="DC.Identifier" content="rzaikconnstrkeywordsperfprop" /> <meta name="DC.Language" content="en-us" /> <!-- All rights reserved. Licensed Materials Property of IBM --> <!-- US Government Users Restricted Rights --> <!-- Use, duplication or disclosure restricted by --> <!-- GSA ADP Schedule Contract with IBM Corp. --> <link rel="stylesheet" type="text/css" href="./ibmdita.css" /> <link rel="stylesheet" type="text/css" href="./ic.css" /> <title>Connection string keywords - Performance properties</title> </head> <body id="rzaikconnstrkeywordsperfprop"><a name="rzaikconnstrkeywordsperfprop"><!-- --></a> <!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script> <h1 class="topictitle1">Connection string keywords - Performance properties</h1> <div><p>Use these iSeries™ Access ODBC driver connection string keywords to change Performance properties of the ODBC connection.</p> <div class="section"><p>The following table lists connection string keywords for Performance properties that are recognized by the iSeries Access ODBC driver:</p> </div> <div class="section"> <div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="border" border="1" rules="all"><caption>Table 1. iSeries Access ODBC connection string keywords for Performance properties</caption><thead align="left"><tr><th align="center" valign="middle" width="21.73913043478261%" id="d0e38">Keyword</th> <th align="center" valign="middle" width="35.177865612648226%" id="d0e40">Description</th> <th align="center" valign="middle" width="33.59683794466403%" id="d0e42">Choices</th> <th align="center" valign="middle" width="9.486166007905137%" id="d0e44">Default</th> </tr> </thead> <tbody><tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">BLOCKFETCH</td> <td valign="top" width="35.177865612648226%" headers="d0e40 ">Specifies whether or not internal blocking will be done on fetches of 1 row. When set, the driver will try to optimize the fetching of records when one record is requested by the application. Multiple records will be retrieved and stored by the driver for later retrieval by the application. When an application requests another row, the driver will not need to send another flow to the host database to get it. If not set, blocking will be used according to the application's ODBC settings for that particular statement. <div class="note"><span class="notetitle">Note:</span> For more information on setting this option see the Fine-tuning record blocking topic.</div> </td> <td valign="top" width="33.59683794466403%" headers="d0e42 ">0 = Use ODBC settings for blocking <p>1 = Use blocking with a fetch of 1 row</p> </td> <td valign="top" width="9.486166007905137%" headers="d0e44 ">1</td> </tr> <tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">BLOCKSIZE or BlockSizeKB</td> <td valign="top" width="35.177865612648226%" headers="d0e40 ">Specifies the block size (in kilobytes) to retrieve from the iSeries server and cache on the client. This property has no effect unless the BLOCKFETCH property is 1. Larger block sizes reduce the frequency of communication to the server, and therefore may increase performance.</td> <td valign="top" width="33.59683794466403%" headers="d0e42 ">1 – 8192</td> <td valign="top" width="9.486166007905137%" headers="d0e44 ">32</td> </tr> <tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">COMPRESSION or AllowDataCompression</td> <td valign="top" width="35.177865612648226%" headers="d0e40 ">Specifies whether to compress data sent to and from the server. In most cases, data compression improves performance due to less data being transmitted between the driver and the server.</td> <td valign="top" width="33.59683794466403%" headers="d0e42 ">0 = Disable compression <p>1 = Enable compression</p> </td> <td valign="top" width="9.486166007905137%" headers="d0e44 ">1</td> </tr> <tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">CONCURRENCY</td> <td valign="top" width="35.177865612648226%" headers="d0e40 ">Specifies whether to override the ODBC concurrency setting by opening all cursors as updateable. <div class="note"><span class="notetitle">Note:</span> In the following two cases, setting this option has no effect: <ol><li>When building a SELECT SQL statement the FOR FETCH ONLY or FOR UPDATE clause can be added. If either of these clauses are present in a SQL statement the ODBC driver will honor the concurrency that is associated with the clause.</li> <li>Catalog result sets are always read-only.</li> </ol> </div> </td> <td valign="top" width="33.59683794466403%" headers="d0e42 ">0 = Use ODBC concurrency settings <p>1 = Open all cursors as updateable</p> </td> <td valign="top" width="9.486166007905137%" headers="d0e44 ">0</td> </tr> <tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">CURSORSENSITIVITY</td> <td valign="top" width="35.177865612648226%" headers="d0e40 ">Specifies the cursor sensitivity to use when opening cursors. This option applies to all forward-only and dynamic cursors that are opened on the same connection. Static cursors are always insensitive. </td> <td valign="top" width="33.59683794466403%" headers="d0e42 ">0 - Unspecified/Asensitive <p>1 = Insensitive</p> <p>2 = Sensitive</p> </td> <td valign="top" width="9.486166007905137%" headers="d0e44 "> </td> </tr> <tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">EXTCOLINFO or ExtendedColInfo</td> <td valign="top" width="35.177865612648226%" headers="d0e40 ">The extended column information affects what the <span class="apiname">SQLGetDescField</span> and <span class="apiname">SQLColAttribute</span> APIs return as Implementation Row Descriptor (IRD) information. The extended column information is available after the SQLPrepare API has been called. The information that is returned is: <ul><li>SQL_DESC_AUTO_UNIQUE_VALUE</li> <li>SQL_DESC_BASE_COLUMN_NAME</li> <li>SQL_DESC_BASE_TABLE_NAME and SQL_DESC_TABLE_NAME</li> <li>SQL_DESC_LABEL</li> <li>SQL_DESC_SCHEMA_NAME</li> <li>SQL_DESC_SEARCHABLE</li> <li> SQL_DESC_UNNAMED</li> <li>SQL_DESC_UPDATABLE</li> </ul> <div class="note"><span class="notetitle">Note:</span> the driver sets the SQL_DESC_AUTO_UNIQUE_VALUE flag only if a column is an identity column with the ALWAYS option over a numeric data type (such as integer). Refer to the DB2<sup>®</sup> UDB SQL Reference for details on identity columns.</div> </td> <td valign="top" width="33.59683794466403%" headers="d0e42 ">0 = Do not retrieve extended column information <p>1 = Retrieve extended column information</p> </td> <td valign="top" width="9.486166007905137%" headers="d0e44 ">0</td> </tr> <tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">LAZYCLOSE</td> <td valign="top" width="35.177865612648226%" headers="d0e40 ">Specifies whether to delay closing cursors until subsequent requests. This will increase overall performance by reducing the total number of requests. <div class="note"><span class="notetitle">Note:</span> This option can cause problems due to the cursors still holding locks on the result set rows after the close request.</div> </td> <td valign="top" width="33.59683794466403%" headers="d0e42 ">0 = Close all cursors immediately <p>1 = Delay closing of cursors until the next request</p> </td> <td valign="top" width="9.486166007905137%" headers="d0e44 ">0</td> </tr> <tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">MAXFIELDLEN or MaxFieldLength</td> <td valign="top" width="35.177865612648226%" headers="d0e40 ">Specifies the maximum LOB (large object) size (in kilobytes) that can be retrieved as part of a result set. LOBs that are larger than this threshold will be retrieved in pieces using extra communication to the server. Larger LOB thresholds will reduce the frequency of communication to the server, but will download more LOB data, even if it is not used. Smaller LOB thresholds may increase frequency of communication to the server, but they will only download LOB data as it is needed. <div class="note"><span class="notetitle">Notes:</span> <img src="./delta.gif" alt="Start of change" /><ul><li>Setting this property to 0 forces the driver to always retrieve the LOB values with additional communication flows. </li> <li>Setting this property larger than 15360 KB has no effect. Anything larger than 15360 KB is retrieved in pieces from the server. Retrieving the data in pieces reduces the amount of memory needed, at any given time, on the client.</li> </ul> <img src="./deltaend.gif" alt="End of change" /></div> </td> <td valign="top" width="33.59683794466403%" headers="d0e42 ">0 — 2097152</td> <td valign="top" width="9.486166007905137%" headers="d0e44 ">32</td> </tr> <tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">PREFETCH</td> <td valign="top" width="35.177865612648226%" headers="d0e40 ">Specifies whether to prefetch data upon executing a SELECT statement. This will increase performance when accessing the initial rows in the ResultSet.</td> <td valign="top" width="33.59683794466403%" headers="d0e42 ">0 = Do not prefetch data <p>1 = Prefetch data</p> </td> <td valign="top" width="9.486166007905137%" headers="d0e44 ">0</td> </tr> <tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">QUERYTIMEOUT</td> <td valign="top" width="35.177865612648226%" headers="d0e40 ">Specifies whether the driver will disable support for the query timeout attribute, SQL_ATTR_QUERY_TIMEOUT. If disabled, SQL queries will run until they finish.</td> <td valign="top" width="33.59683794466403%" headers="d0e42 ">0 = Disable support for the query timeout attribute <p>1 = Allow the query timeout attribute to be set</p> </td> <td valign="top" width="9.486166007905137%" headers="d0e44 ">1</td> </tr> </tbody> </table> </div> </div> </div> <div> <div class="familylinks"> <div class="parentlink"><strong>Parent topic:</strong> <a href="connectkeywords.htm" title="The iSeries Access ODBC driver has many connection string keywords that can be used to change the behavior of the ODBC connection.">Connection string keywords</a></div> </div> <div class="relref"><strong>Related reference</strong><br /> <div><a href="odbcfinetunercdblock.htm" title="Record-blocking is a technique that significantly reduces the number of network flows.">Fine-tune record-blocking</a></div> </div> </div> </body> </html>