115 lines
5.3 KiB
HTML
115 lines
5.3 KiB
HTML
<!--$Id: rep_request.html 63573 2008-05-23 21:43:21Z trent.nelson $-->
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<!--Copyright (c) 1997,2008 Oracle. All rights reserved.-->
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<!--See the file LICENSE for redistribution information.-->
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<html>
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<head>
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<title>Berkeley DB: DbEnv::rep_set_request</title>
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<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
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<meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++">
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</head>
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<body bgcolor=white>
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<table width="100%"><tr valign=top>
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<td>
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<b>DbEnv::rep_set_request</b>
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</td>
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<td align=right>
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<a href="../api_cxx/api_core.html"><img src="../images/api.gif" alt="API"></a>
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<a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a></td>
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</tr></table>
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<hr size=1 noshade>
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<tt>
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<b><pre>
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#include <db_cxx.h>
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<p>
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int
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DbEnv::rep_set_request(u_int32_t min, u_int32_t max);
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<p>
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int
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DbEnv::rep_get_request(u_int32_t *minp, u_int32_t *maxp);
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</pre></b>
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<hr size=1 noshade>
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<b>Description: DbEnv::rep_set_request</b>
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<p>The DbEnv::rep_set_request method sets a threshold for the minimum and maximum
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time that a client waits before requesting retransmission of a missing
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message. Specifically, if the client detects a gap in the sequence
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of incoming log records or database pages, Berkeley DB will
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wait for at least <b>min</b> microseconds before requesting
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retransmission of the missing record. Berkeley DB will double that
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amount before requesting the same missing record again, and so on, up
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to a maximum threshold of <b>max</b> microseconds.</p>
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<p>These values are thresholds only. Since Berkeley DB has no thread available in
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the library as a timer, the threshold is only checked when a thread
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enters the Berkeley DB library to process an incoming replication message.
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Any amount of time may have passed since the last message arrived and
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Berkeley DB only checks whether the amount of time since a request was made
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is beyond the threshold value or not.</p>
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<p>By default the minimum is 40000 and the maximum is 1280000 (1.28 seconds).
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These defaults are fairly arbitrary and the application likely needs
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to adjust these. The values should be based on expected load and
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performance characteristics of the master and client host platforms
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and transport infrastructure as well as round-trip message time.</p>
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<p>The database environment's replication subsystem may also be configured using the
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environment's <a href="../ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file. The syntax of the entry in that
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file is a single line with the string "rep_set_request", one or more whitespace
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characters, and the request times specified in two parts: the min and the max.
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For example, "rep_set_request 40000 1280000".
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Because the <a href="../ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file is read when the database environment
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is opened, it will silently overrule configuration done before that
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time.</p>
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<p>The DbEnv::rep_set_request method configures a database environment, not only operations
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performed using the specified <a href="../api_cxx/env_class.html">DbEnv</a> handle.</p>
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<p>The DbEnv::rep_set_request method may be called at any time during the life of the
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application.</p>
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<p>The DbEnv::rep_set_request method
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either returns a non-zero error value
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or throws an exception that encapsulates a non-zero error value on
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failure, and returns 0 on success.
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</p>
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<b>Parameters</b> <br>
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<b>max</b><ul compact><li>The maximum number of microseconds a client waits before
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requesting retransmission.</ul>
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<b>min</b><ul compact><li>The minimum number of microseconds a client waits before
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requesting retransmission.</ul>
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<br>
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<br><b>Errors</b>
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<p>The DbEnv::rep_set_request method
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may fail and throw
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<a href="../api_cxx/except_class.html">DbException</a>,
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encapsulating one of the following non-zero errors, or return one of
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the following non-zero errors:</p>
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<br>
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<b>EINVAL</b><ul compact><li>An
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invalid flag value or parameter was specified.</ul>
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<br>
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<hr size=1 noshade>
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<b>Description: DbEnv::rep_get_request</b>
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<p>The DbEnv::rep_get_request method returns the minimum and maximum number of
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microseconds a client waits before requesting retransmission.</p>
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<p>The DbEnv::rep_get_request method may be called at any time during the life of the
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application.</p>
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<p>The DbEnv::rep_get_request method
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either returns a non-zero error value
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or throws an exception that encapsulates a non-zero error value on
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failure, and returns 0 on success.
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</p>
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<b>Parameters</b> <br>
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<b>maxp</b><ul compact><li>The <b>maxp</b> parameter references memory into which
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the maximum number of microseconds a client will wait before requesting
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retransmission is copied.</ul>
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<b>minp</b><ul compact><li>The <b>minp</b> parameter references memory into which
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the minimum number of microseconds a client will wait before requesting
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retransmission is copied.</ul>
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<br>
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<hr size=1 noshade>
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<br><b>Class</b>
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<a href="../api_cxx/env_class.html">DbEnv</a>
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<br><b>See Also</b>
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<a href="../api_cxx/rep_list.html">Replication and Related Methods</a>
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</tt>
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<table width="100%"><tr><td><br></td><td align=right>
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<a href="../api_cxx/api_core.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a>
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</td></tr></table>
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<p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font>
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</body>
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