109 lines
5.3 KiB
HTML
109 lines
5.3 KiB
HTML
<!--$Id: rep_clockskew.html 63573 2008-05-23 21:43:21Z trent.nelson $-->
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FOOO
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<html>
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<head>
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<title>Berkeley DB: DbEnv::rep_set_clockskew</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_clockskew</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_clockskew(u_int32_t fast_clock, u_int32_t slow_clock);
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<p>
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DbEnv::rep_get_clockskew(u_int32_t *fast_clockp, u_in32_t *slow_clockp);
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</pre></b>
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<hr size=1 noshade>
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<b>Description: DbEnv::rep_set_clockskew</b>
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<p>The DbEnv::rep_set_clockskew method sets the clock skew ratio among
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replication group members based on the fastest and slowest measurements
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among the group for use with master leases. Calling this method is
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optional, the default values for clock skew assume no skew. The user
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must also configure leases via the <a href="../api_cxx/rep_config.html">DbEnv::rep_set_config</a> method.
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Additionally, the user must also set the master lease timeout via the
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<a href="../api_cxx/rep_timeout.html">DbEnv::rep_set_timeout</a> method and the number of sites in the replication
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group via the <a href="../api_cxx/rep_nsites.html">DbEnv::rep_set_nsites</a> method. These methods may be called in
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any order. For a description of the clock skew values, see
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<a href="../ref/rep/clock_skew.html">Clock skew</a>. For a description
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of master leases, see <a href="../ref/rep/lease.html">Master
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leases</a>.</p>
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<p>These arguments can be used to express either raw measurements of a
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clock timing experiment or a percentage across machines. For instance
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a group of sites have a 2% variance, then <b>fast_clock</b> should be
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given as 102, and <b>slow_clock</b> should be set at 100. Or, for a
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0.03% difference, you can use 10003 and 10000 respectively.</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_clockskew", one or more whitespace
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characters, and the clockskew specified in two parts: the fast_clock and the slow_clock.
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For example, "rep_set_clockskew 102 100".
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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_clockskew 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_clockskew method may not be called after the <a href="../api_cxx/repmgr_start.html">DbEnv::repmgr_start</a> or <a href="../api_cxx/rep_start.html">DbEnv::rep_start</a> methods are
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called.</p>
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<p>The DbEnv::rep_set_clockskew 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>fast_clock</b><ul compact><li>The value, relative to the <b>slow_clock</b>, of the fastest clock
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in the group of sites.</ul>
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<b>slow_clock</b><ul compact><li>The value of the slowest clock in the group of sites.</ul>
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<br>
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<br><b>Errors</b>
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<p>The DbEnv::rep_set_clockskew 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_clockskew</b>
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<p>The DbEnv::rep_get_clockskew method returns the current clock skew values.</p>
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<p>The DbEnv::rep_get_clockskew 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_clockskew 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>fast_clockp</b><ul compact><li>The <b>fast_clockp</b> parameter references memory into which
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the value for the fastest clock in the group of sites is copied.</ul>
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<b>slow_clockp</b><ul compact><li>The <b>slow_clockp</b> parameter references memory into which
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the value for the slowest clock in the group of sites 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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