configure-replica-set-secondary-sync-target.txt

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Configure a Secondary's Sync Target
===================================

.. default-domain:: mongodb

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Overview
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Secondaries capture data from the primary member to maintain an up to date
copy of the sets' data. However, by default secondaries may automatically
change their sync targets to secondary members based on changes in the
ping time between members and the state of other members’ replication. See
:doc:`/core/replica-set-sync` and
:doc:`/tutorial/manage-chained-replication` for more information.

For some deployments, implementing a custom replication sync topology may
be more effective than the default sync target selection logic. MongoDB
provides the ability to specify a host to use as a sync target.

To temporarily override the default sync target selection logic, you
may manually configure a :term:`secondary` member's sync target to
temporarily pull :term:`oplog` entries. The following provide access to
this functionality:

- :dbcommand:`replSetSyncFrom` command, or

- :method:`rs.syncFrom()` helper in the :program:`mongo` shell

Considerations
--------------

.. include:: /includes/extracts/rsSyncFrom-behavior-both.rst

Procedure
---------

To use the :dbcommand:`replSetSyncFrom` command in the :program:`mongo` shell:

.. code-block:: javascript

   db.adminCommand( { replSetSyncFrom: "hostname<:port>" } );

To use the :method:`rs.syncFrom()` helper in the :program:`mongo` shell:

.. code-block:: javascript

   rs.syncFrom("hostname<:port>");