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< p > Library Version 11.2.5.3< / p >
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< th colspan = "3" align = "center" > DB_ENV-> rep_set_config()< / th >
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Replication Methods
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< h2 class = "title" style = "clear: both" > < a id = "repconfig" > < / a > DB_ENV-> rep_set_config()< / h2 >
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< pre class = "programlisting" > #include < db.h>
int
DB_ENV-> rep_set_config(DB_ENV *env, u_int32_t which, int onoff); < / pre >
< p >
The < code class = "methodname" > DB_ENV-> rep_set_config()< / code > method configures the Berkeley DB
replication subsystem.
< / 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_config", one or more whitespace characters, and the
method < span class = "bold" > < strong > which< / strong > < / span > parameter as a
string and optionally one or more whitespace characters, and the
string "on" or "off". If the optional string is omitted, the
default is "on"; for example, "rep_set_config DB_REP_CONF_NOWAIT"
or "rep_set_config DB_REP_CONF_NOWAIT on". 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.
< / p >
< p >
The < code class = "methodname" > DB_ENV-> rep_set_config()< / code > method configures a database
environment, not only operations performed using the specified
< a class = "link" href = "env.html" title = "Chapter > DB_ENV< / a > handle.
< / p >
< p >
The < code class = "methodname" > DB_ENV-> rep_set_config()< / code > method may not be
called to set in-memory replication after the environment is
opened using the
< a class = "xref" href = "envopen.html" title = "DB_ENV->open()" > DB_ENV-> open()< / a > method.
This method may also not be called to set master leases after the
< a class = "xref" href = "repstart.html" title = "DB_ENV->rep_start()" > DB_ENV-> rep_start()< / a > or
< a class = "xref" href = "repmgrstart.html" title = "DB_ENV->repmgr_start()" > DB_ENV-> repmgr_start()< / a > methods
are called. For all other < span class = "bold" > < strong > which< / strong > < / span >
parameters, this method may be called at any time during the life
of the application.
< / p >
< p >
The < code class = "methodname" > DB_ENV-> rep_set_config()< / code > < span >
< span >
method returns a non-zero error value on failure and 0 on success.
< / span >
< / span >
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< h3 class = "title" > < a id = "idp62067368" > < / a > Parameters< / h3 >
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< h4 class = "title" > < a id = "idp62002696" > < / a > which< / h4 >
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The < span class = "bold" > < strong > which< / strong > < / span > parameter must be set to
one of the following values:
< / p >
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< p > < a id = "config_DB_REP_CONF_AUTOINIT" > < / a >
< code class = "literal" > DB_REP_CONF_AUTOINIT< / code >
< / p >
< p >
The replication master will automatically re-initialize outdated
clients. This option is turned on by default.
< / p >
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< li >
< p > < a id = "config_DB_REP_CONF_BULK" > < / a >
< code class = "literal" > DB_REP_CONF_BULK< / code >
< / p >
< p >
The replication master sends groups of records to the clients in a
single network transfer.
< / p >
< / li >
< li >
< p > < a id = "config_DB_REP_CONF_DELAYCLIENT" > < / a >
< code class = "literal" > DB_REP_CONF_DELAYCLIENT< / code >
< / p >
< p >
The client should delay synchronizing to a newly declared master.
Clients configured in this way will remain
unsynchronized until the application calls the
< a class = "xref" href = "repsync.html" title = "DB_ENV->rep_sync()" > DB_ENV-> rep_sync()< / a > method.
< / p >
< / li >
< li >
< p > < a id = "config_DB_REP_CONF_INMEM" > < / a >
< code class = "literal" > DB_REP_CONF_INMEM< / code >
< / p >
< p >
Store internal replication information in memory only.
< / p >
< p >
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By default, replication creates files in the
environment home directory to preserve some
internal information. If this configuration flag is
turned on, replication only stores this internal
information in-memory and cannot keep persistent
state across a site crash or reboot. This results
in the following limitations:
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< / p >
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A master site should not reappoint itself
master immediately after crashing or
rebooting because the application would
incur a slightly higher risk of client
crashes. The former master site should
rejoin the replication group as a client.
The application should either hold an
election or appoint a different site to be
the next master.
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< / p >
< / li >
< li >
< p >
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An application has a slightly higher risk
that elections will fail or be unable to
complete. Calling additional elections
should eventually yield a winner.
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< / p >
< / li >
< li >
< p >
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An application has a slight risk that the
wrong site may win an election, resulting
in the loss of some data. This is
consistent with the general loss of data
durability when running in-memory.
< / p >
< / li >
< li >
< p >
Replication Manager applications will no
longer maintain group membership
information persistently on-disk. For more
information, see < a href = "../../programmer_reference/rep_filename.html" class = "olink" > Managing Replication Files< / a > in the
< em class = "citetitle" > Berkeley DB Programmer's Reference Guide< / em > .
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< / p >
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< p >
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This configuration flag can only be turned on
before the environment is opened with the
< a class = "xref" href = "envopen.html" title = "DB_ENV->open()" > DB_ENV-> open()< / a >
method. Its value cannot be changed while the
environment is open. All sites in the replication
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group should have the same value for this
configuration flag.
< / p >
< / li >
< li >
< p >
< code class = "literal" > DB_REP_CONF_LEASE< / code >
< / p >
< p >
Master leases will be used for this site.
< / p >
< p >
Configuring this option may result in
< code class = "literal" > DB_REP_LEASE_EXPIRED< / code > error returns
from the < a class = "xref" href = "dbget.html" title = "DB->get()" > DB-> get()< / a > and
< a class = "xref" href = "dbcget.html" title = "DBcursor->get()" > DBcursor-> get()< / a > methods
when attempting to read entries from a database after the site's
master lease has expired.
< / p >
< p >
This configuration flag may not be set after the
< a class = "xref" href = "repmgrstart.html" title = "DB_ENV->repmgr_start()" > DB_ENV-> repmgr_start()< / a > method or the
< a class = "xref" href = "repstart.html" title = "DB_ENV->rep_start()" > DB_ENV-> rep_start()< / a >
method is called. All sites in the replication
group should have the same value for this
configuration flag.
< / p >
< / li >
< li >
< p > < a id = "config_DB_REP_CONF_NOWAIT" > < / a >
< code class = "literal" > DB_REP_CONF_NOWAIT< / code >
< / p >
< p >
Berkeley DB method calls that would normally block while clients are
in recovery will return errors immediately.
< / p >
< / li >
< li >
< p > < a id = "config_DB_REPMGR_CONF_ELECTIONS" > < / a >
< code class = "literal" > DB_REPMGR_CONF_ELECTIONS< / code >
< / p >
< p >
Replication Manager automatically runs elections to
choose a new master when the old master appears to
have become disconnected. This option is turned on
by default.
< / p >
< p >
If this option is turned off, the application is
responsible for assigning the new master
explicitly, by calling the
< code class = "methodname" > DB_ENV-> repmgr_start()< / code >
method.
< / p >
< div class = "caution" style = "margin-left: 0.5in; margin-right: 0.5in;" >
< h3 class = "title" > Caution< / h3 >
< p >
Most Replication Manager
applications should accept the default automatic
behavior. Allowing two sites in a replication
group to act as master simultaneously can lead to
loss of data.
< / p >
< / div >
< p >
In an application with multiple processes per
database environment, only the main replication
process may change this configuration setting.
< / p >
< / li >
< li >
< p > < a id = "config_DB_REPMGR_CONF_2SITE_STRICT" > < / a >
< code class = "literal" > DB_REPMGR_CONF_2SITE_STRICT< / code >
< / p >
< p >
Replication Manager observes the strict "majority" rule in managing
elections, even in a group with only 2 sites. This means the client
in a 2-site group will be unable to take over as master if the
original master fails or becomes disconnected. (See the
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< a href = "../../programmer_reference/rep_twosite.html" class = "olink" >
Special considerations for two-site replication groups
< / a >
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section in the < em class = "citetitle" > Berkeley DB Programmer's Reference Guide< / em > for more information.)
Both sites in the replication group should have the same value for this
configuration flag. This option is turned on by
default.
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< div >
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< h4 class = "title" > < a id = "idp62095944" > < / a > onoff< / h4 >
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< / div >
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< p >
If the < span class = "bold" > < strong > onoff< / strong > < / span > parameter
is zero, the configuration flag is turned off.
Otherwise, it is turned on. Most configuration flags are
turned off by default, exceptions are noted above.
< / p >
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< h3 class = "title" > < a id = "idp62075080" > < / a > Errors< / h3 >
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< / div >
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< p >
The < code class = "methodname" > DB_ENV-> rep_set_config()< / code > < span >
< span >
method may fail and return one of the following non-zero errors:
< / span >
< / span >
< / p >
< div class = "sect3" lang = "en" xml:lang = "en" >
< div class = "titlepage" >
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< div >
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< h4 class = "title" > < a id = "idp62086520" > < / a > EINVAL< / h4 >
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< p >
If setting in-memory replication after the database environment is already
opened; if setting master leases after replication is started; if setting
the 2-site strict majority rule for a Base API application;
or if an invalid flag value or parameter was specified.
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< h3 class = "title" > < a id = "idp62078040" > < / a > Class< / h3 >
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< p >
< a class = "link" href = "env.html" title = "Chapter > DB_ENV< / a >
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< h3 class = "title" > < a id = "idp62025768" > < / a > See Also< / h3 >
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< p >
< a class = "xref" href = "rep.html#replist" title = "Replication and Related Methods" > Replication and Related Methods< / a >
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