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<meta name="DC.Title" content="Connection string keywords - Performance properties" />
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<meta name="abstract" content="Use these iSeries Access ODBC driver connection string keywords to change Performance properties of the ODBC connection." />
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Connection string keywords - Performance properties</h1>
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<div><p>Use these iSeries™ Access ODBC driver connection string keywords
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to change Performance properties of the ODBC connection.</p>
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<div class="section"><p>The following table lists connection string keywords for Performance
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properties that are recognized by the iSeries Access ODBC driver:</p>
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</div>
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<div class="section">
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<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
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Performance properties</caption><thead align="left"><tr><th align="center" valign="middle" width="21.73913043478261%" id="d0e38">Keyword</th>
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<th align="center" valign="middle" width="35.177865612648226%" id="d0e40">Description</th>
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<th align="center" valign="middle" width="33.59683794466403%" id="d0e42">Choices</th>
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<th align="center" valign="middle" width="9.486166007905137%" id="d0e44">Default</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">BLOCKFETCH</td>
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<td valign="top" width="35.177865612648226%" headers="d0e40 ">Specifies whether or not internal blocking will be done
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on fetches of 1 row. When set, the driver will try to optimize the fetching
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of records when one record is requested by the application. Multiple records
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will be retrieved and stored by the driver for later retrieval by the application.
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When an application requests another row, the driver will not need to send
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another flow to the host database to get it. If not set, blocking will be
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used according to the application's ODBC settings for that particular statement. <div class="note"><span class="notetitle">Note:</span> For
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more information on setting this option see the Fine-tuning record blocking
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topic.</div>
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</td>
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<td valign="top" width="33.59683794466403%" headers="d0e42 ">0 = Use ODBC settings for blocking <p>1 = Use blocking
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with a fetch of 1 row</p>
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</td>
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<td valign="top" width="9.486166007905137%" headers="d0e44 ">1</td>
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</tr>
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<tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">BLOCKSIZE or BlockSizeKB</td>
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<td valign="top" width="35.177865612648226%" headers="d0e40 ">Specifies the block size (in kilobytes) to retrieve
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from the iSeries server
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and cache on the client. This property has no effect unless the BLOCKFETCH
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property is 1. Larger block sizes reduce the frequency of communication to
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the server, and therefore may increase performance.</td>
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<td valign="top" width="33.59683794466403%" headers="d0e42 ">1 – 8192</td>
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<td valign="top" width="9.486166007905137%" headers="d0e44 ">32</td>
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</tr>
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<tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">COMPRESSION or AllowDataCompression</td>
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<td valign="top" width="35.177865612648226%" headers="d0e40 ">Specifies whether to compress data sent to and from
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the server. In most cases, data compression improves performance due to less
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data being transmitted between the driver and the server.</td>
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<td valign="top" width="33.59683794466403%" headers="d0e42 ">0 = Disable compression <p>1 = Enable compression</p>
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</td>
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<td valign="top" width="9.486166007905137%" headers="d0e44 ">1</td>
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</tr>
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<tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">CONCURRENCY</td>
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<td valign="top" width="35.177865612648226%" headers="d0e40 ">Specifies whether to override the ODBC concurrency setting
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by opening all cursors as updateable. <div class="note"><span class="notetitle">Note:</span> In the following two cases, setting
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this option has no effect: <ol><li>When building a SELECT SQL statement the FOR FETCH ONLY or FOR UPDATE
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clause can be added. If either of these clauses are present in a SQL statement
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the ODBC driver will honor the concurrency that is associated with the clause.</li>
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<li>Catalog result sets are always read-only.</li>
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</ol>
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</div>
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</td>
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<td valign="top" width="33.59683794466403%" headers="d0e42 ">0 = Use ODBC concurrency settings <p>1 = Open all cursors
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as updateable</p>
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</td>
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<td valign="top" width="9.486166007905137%" headers="d0e44 ">0</td>
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</tr>
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<tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">CURSORSENSITIVITY</td>
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<td valign="top" width="35.177865612648226%" headers="d0e40 ">Specifies the cursor sensitivity to use when opening
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cursors. This option applies to all forward-only and dynamic cursors that
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are opened on the same connection. Static cursors are always insensitive. </td>
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<td valign="top" width="33.59683794466403%" headers="d0e42 ">0 - Unspecified/Asensitive <p>1 = Insensitive</p>
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<p>2
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= Sensitive</p>
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</td>
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<td valign="top" width="9.486166007905137%" headers="d0e44 "> </td>
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</tr>
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<tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">EXTCOLINFO or ExtendedColInfo</td>
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<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
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return as Implementation Row Descriptor (IRD) information. The extended column
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information is available after the SQLPrepare API has been called. The information
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that is returned is: <ul><li>SQL_DESC_AUTO_UNIQUE_VALUE</li>
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<li>SQL_DESC_BASE_COLUMN_NAME</li>
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<li>SQL_DESC_BASE_TABLE_NAME and SQL_DESC_TABLE_NAME</li>
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<li>SQL_DESC_LABEL</li>
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<li>SQL_DESC_SCHEMA_NAME</li>
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<li>SQL_DESC_SEARCHABLE</li>
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<li> SQL_DESC_UNNAMED</li>
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<li>SQL_DESC_UPDATABLE</li>
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</ul>
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<div class="note"><span class="notetitle">Note:</span> the driver sets the SQL_DESC_AUTO_UNIQUE_VALUE flag only if a column
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is an identity column with the ALWAYS option over a numeric data type (such
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as integer). Refer to the DB2<sup>®</sup> UDB SQL Reference for details on identity columns.</div>
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</td>
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<td valign="top" width="33.59683794466403%" headers="d0e42 ">0 = Do not retrieve extended column information <p>1
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= Retrieve extended column information</p>
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</td>
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<td valign="top" width="9.486166007905137%" headers="d0e44 ">0</td>
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</tr>
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<tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">LAZYCLOSE</td>
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<td valign="top" width="35.177865612648226%" headers="d0e40 ">Specifies whether to delay closing cursors until subsequent
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requests. This will increase overall performance by reducing the total number
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of requests. <div class="note"><span class="notetitle">Note:</span> This option can cause problems due to the cursors still
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holding locks on the result set rows after the close request.</div>
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</td>
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<td valign="top" width="33.59683794466403%" headers="d0e42 ">0 = Close all cursors immediately <p>1 = Delay closing
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of cursors until the next request</p>
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</td>
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<td valign="top" width="9.486166007905137%" headers="d0e44 ">0</td>
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</tr>
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<tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">MAXFIELDLEN or MaxFieldLength</td>
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<td valign="top" width="35.177865612648226%" headers="d0e40 ">Specifies the maximum LOB (large object) size (in kilobytes)
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that can be retrieved as part of a result set. LOBs that are larger than this
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threshold will be retrieved in pieces using extra communication to the server.
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Larger LOB thresholds will reduce the frequency of communication to the server,
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but will download more LOB data, even if it is not used. Smaller LOB thresholds
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may increase frequency of communication to the server, but they will only
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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
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values with additional communication flows. </li>
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<li>Setting this property larger than 15360 KB has no effect. Anything larger
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than 15360 KB is retrieved in pieces from the server. Retrieving the data
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in pieces reduces the amount of memory needed, at any given time, on the client.</li>
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</ul>
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<img src="./deltaend.gif" alt="End of change" /></div>
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</td>
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<td valign="top" width="33.59683794466403%" headers="d0e42 ">0 — 2097152</td>
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<td valign="top" width="9.486166007905137%" headers="d0e44 ">32</td>
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</tr>
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<tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">PREFETCH</td>
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<td valign="top" width="35.177865612648226%" headers="d0e40 ">Specifies whether to prefetch data upon executing a
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SELECT statement. This will increase performance when accessing the initial
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rows in the ResultSet.</td>
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<td valign="top" width="33.59683794466403%" headers="d0e42 ">0 = Do not prefetch data <p>1 = Prefetch data</p>
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</td>
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<td valign="top" width="9.486166007905137%" headers="d0e44 ">0</td>
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</tr>
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<tr><td valign="top" width="21.73913043478261%" headers="d0e38 ">QUERYTIMEOUT</td>
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<td valign="top" width="35.177865612648226%" headers="d0e40 ">Specifies whether the driver will disable support for
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the query timeout attribute, SQL_ATTR_QUERY_TIMEOUT. If disabled, SQL queries
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will run until they finish.</td>
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<td valign="top" width="33.59683794466403%" headers="d0e42 ">0 = Disable support for the query timeout attribute <p>1
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= Allow the query timeout attribute to be set</p>
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</td>
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<td valign="top" width="9.486166007905137%" headers="d0e44 ">1</td>
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</tr>
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</tbody>
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</table>
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</div>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<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>
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</div>
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<div class="relref"><strong>Related reference</strong><br />
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<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>
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</div>
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