79 lines
5.3 KiB
HTML
79 lines
5.3 KiB
HTML
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<meta name="DC.Title" content="Initialization and termination tasks in a DB2 UDB CLI application" />
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<meta name="abstract" content="The initialization task allocates and initializes environment handles and connection handles." />
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<meta name="description" content="The initialization task allocates and initializes environment handles and connection handles." />
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<meta name="DC.subject" content="initialization, termination, SQLAllocConnect, function, overview, SQLAllocEnv, function, SQLConnect, function, SQLDisconnect, function, SQLFreeConnect, function, SQLFreeEnv, function" />
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<meta name="keywords" content="initialization, termination, SQLAllocConnect, function, overview, SQLAllocEnv, function, SQLConnect, function, SQLDisconnect, function, SQLFreeConnect, function, SQLFreeEnv, function" />
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<title>Initialization and termination tasks in a DB2 UDB CLI application</title>
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</head>
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<body id="rzadphditerm"><a name="rzadphditerm"><!-- --></a>
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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">Initialization and termination tasks in a DB2 UDB CLI application</h1>
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<div><p>The initialization task allocates and initializes environment handles
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and connection handles.</p>
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<p>The following figure shows the function call sequences for both the initialization
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and termination tasks. The transaction processing task in the middle of the
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diagram is shown in <a href="rzadphdptran.htm#rzadphdptran">Transaction processing task in a DB2 UDB CLI application</a>.</p>
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<div class="fignone" id="rzadphditerm__fgovvb"><a name="rzadphditerm__fgovvb"><!-- --></a><span class="figcap">Figure 1. Conceptual view of initialization and termination
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tasks</span><br /><img src="rv3w322.gif" alt="Conceptual view of initialization
and termination task" /><br /></div>
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<div class="p">The termination task frees handles. A handle is a variable
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that refers to a data object that is controlled by DB2<sup>®</sup> UDB CLI. Using handles frees the application
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from having to allocate and manage global variables or data structures, such
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as the SQL descriptor area (SQLDA), or SQL communication area (SQLCA) used
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in embedded SQL interfaces for IBM<sup>®</sup> Database Management Systems (DBMSs).
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An application then passes the appropriate handle when it calls other DB2 UDB
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CLI functions. Here are the types of handles: <dl><dt class="dlterm">Environment handle </dt>
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<dd>The environment handle refers
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to the data object that contains global information regarding the state of
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the application. This handle is allocated by calling <samp class="codeph">SQLAllocEnv()</samp>,
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and freed by calling <samp class="codeph">SQLFreeEnv()</samp>. An environment handle
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must be allocated before a connection handle can be allocated. Only one environment
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handle can be allocated per application.</dd>
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<dt class="dlterm">Connection handle</dt>
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<dd>A connection handle refers
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to a data object that contains information that is associated with a connection
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that is managed by DB2 UDB CLI. This includes general status information,
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transaction status, and diagnostic information. Each connection handle is
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allocated by calling <samp class="codeph">SQLAllocConnect()</samp> and freed by calling <samp class="codeph">SQLFreeConnect()</samp>.
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An application must allocate a connection handle for each connection to a
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database server.</dd>
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<dt class="dlterm">Statement handle</dt>
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<dd>Statement handles are discussed in <a href="rzadphdptran.htm">Transaction
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processing task in a DB2 UDB CLI application</a>.</dd>
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</dl>
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</div>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="rzadpexiniterm.htm">Example: Initialization and connection in a DB2 UDB CLI application</a></strong><br />
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</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzadphdovv.htm" title="Find out how you code your applications to use the DB2 CLI functions.">Write a DB2 UDB CLI application</a></div>
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</div>
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</div>
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</body>
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</html>
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