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< th colspan = "3" align = "center" > DbEnv::rep_set_clockskew()< / th >
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Replication Methods
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< h2 class = "title" style = "clear: both" > < a id = "repclockskew" > < / a > DbEnv::rep_set_clockskew()< / h2 >
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< pre class = "programlisting" > #include < db_cxx.h>
int
DbEnv::rep_set_clockskew(u_int32_t fast_clock, u_int32_t slow_clock); < / pre >
< p >
The < code class = "methodname" > DbEnv::rep_set_clockskew()< / code > method sets the
clock skew ratio among replication group members based on the fastest
and slowest measurements among the group for use with master leases.
Calling this method is optional; the default values for clock skew
assume no skew. The user must also configure leases via the
< a class = "xref" href = "repconfig.html" title = "DbEnv::rep_set_config()" > DbEnv::rep_set_config()< / a >
method. Additionally, the user must also set the master lease timeout
via the
< a class = "xref" href = "repset_timeout.html" title = "DbEnv::rep_set_timeout()" > DbEnv::rep_set_timeout()< / a >
method. For Base API applications, the user must also set the number of
sites in the replication group via the
< a class = "xref" href = "repnsites.html" title = "DbEnv::rep_set_nsites()" > DbEnv::rep_set_nsites()< / a >
method. These methods may be called in any order. For a description
of the clock skew values, see
< a href = "../../programmer_reference/rep_clock_skew.html" class = "olink" > Clock skew< / a >
in the < em class = "citetitle" > Berkeley DB Programmer's Reference Guide< / em > . For a description of
master leases, see
< a href = "../../programmer_reference/rep_lease.html" class = "olink" > Master leases< / a > in the
< em class = "citetitle" > Berkeley DB Programmer's Reference Guide< / em > .
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< p >
These arguments can be used to express either raw measurements of a
clock timing experiment or a percentage across machines. For example, if
a group of sites has a 2% variance, then < span class = "bold" > < strong > fast_clock< / strong > < / span > should be set to 102, and
< span class = "bold" > < strong > slow_clock< / strong > < / span > should be set to 100. Or,
for a 0.03% difference, you can use 10003 and 10000 respectively.
< / p >
< p >
The database environment's replication subsystem may also be
configured using the environment's < a href = "../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class = "olink" > DB_CONFIG< / a > file. The syntax of
the entry in that file is a single line with the string
"rep_set_clockskew", one or more whitespace characters, and the
clockskew specified in two parts: the fast_clock and the
slow_clock. For example, "rep_set_clockskew 102 100". Because the
< a href = "../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class = "olink" > DB_CONFIG< / a > file is read when the database environment is opened,
it will silently overrule configuration done before that time.
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The < code class = "methodname" > DbEnv::rep_set_clockskew()< / code > method configures a database
environment, not only operations performed using the specified
< a class = "link" href = "env.html" title = "Chapter > DbEnv< / a > handle.
< / p >
< p >
The < code class = "methodname" > DbEnv::rep_set_clockskew()< / code > method may not be called after the
< a class = "xref" href = "repmgrstart.html" title = "DbEnv::repmgr_start()" > DbEnv::repmgr_start()< / a > or
< a class = "xref" href = "repstart.html" title = "DbEnv::rep_start()" > DbEnv::rep_start()< / a >
methods are called.
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The < code class = "methodname" > DbEnv::rep_set_clockskew()< / code > < span >
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method either returns a non-zero error value or throws an
exception that encapsulates a non-zero error value on
failure, and returns 0 on success.
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< h3 class = "title" > < a id = "id3639664" > < / a > Parameters< / h3 >
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< h4 class = "title" > < a id = "id3639656" > < / a > fast_clock< / h4 >
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The value, relative to the < span class = "bold" > < strong > slow_clock< / strong > < / span > ,
of the fastest clock in the group of sites.
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< h4 class = "title" > < a id = "id3639460" > < / a > slow_clock< / h4 >
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The value of the slowest clock in the group of sites.
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< h3 class = "title" > < a id = "id3639064" > < / a > Errors< / h3 >
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The < code class = "methodname" > DbEnv::rep_set_clockskew()< / code > < span >
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method may fail and throw a < a class = "link" href = "dbexception.html" title = "Chapter > DbException< / a >
exception, encapsulating one of the following non-zero errors, or return one
of the following non-zero errors:
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< h4 class = "title" > < a id = "id3639872" > < / a > EINVAL< / h4 >
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If the method was called after replication is started with a
call to the
< a class = "xref" href = "repmgrstart.html" title = "DbEnv::repmgr_start()" > DbEnv::repmgr_start()< / a > or the
< a class = "xref" href = "repstart.html" title = "DbEnv::rep_start()" > DbEnv::rep_start()< / a > method; or if
an invalid flag value or parameter was specified.
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< h3 class = "title" > < a id = "id3639668" > < / a > See Also< / h3 >
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< a class = "xref" href = "rep.html#replist" title = "Replication and Related Methods" > Replication and Related Methods< / a >
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