db.cloneDatabase()¶

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Definition
Behavior
Example

Definition¶

db.cloneDatabase("hostname")¶

Deprecated since version 4.0: MongoDB deprecates clone and its helper db.cloneDatabase(). For information on alternatives, see copydb and clone Commands.

Copies a remote database to the current database. The command assumes that the remote database has the same name as the current database.

Parameter	Type	Description
`hostname`	string	The hostname of the database to copy.

This method provides a wrapper around the clone command.

Behavior¶

Data¶

The db.cloneDatabase() method does not snapshot the database. If any clients update the database you’re copying at any point during the clone operation, the resulting database may be inconsistent.

Locks¶

The destination database will be locked periodically during the clone operation. In other words, db.cloneDatabase() will occasionally yield to allow other operations on the database to complete.

FeatureCompatibilityVersion¶

You cannot copy data between a MongoDB 4.0 mongod instance with featureCompatibilityVersion (FCV) 4.0 and a MongoDB version 3.6 mongod instance.

Note

You cannot copy data between a MongoDB 4.0 mongod instance (regardless of the FCV value) and a MongoDB 3.4 and earlier mongod instance.

For example:

Instance 1	Instance 2
Version 4.0 `mongod` with FCV 4.0	Version 4.0 `mongod` with FCV 4.0	Can copy data.
Version 4.0 `mongod` with FCV 4.0	Version 4.0 `mongod` with FCV 3.6	Can copy data.
Version 4.0 `mongod` with FCV 4.0	Version 3.6 `mongod` with FCV 3.6	Cannot copy data. Instance 2 must be a MongoDB version 4.0
Version 4.0 `mongod` with FCV 3.6	Version 3.6 `mongod` with FCV 3.6	Can copy data.
Version 4.0 `mongod` with FCV 3.6	Version 3.6 `mongod` with FCV 3.4	Can copy data.

In general, if the mongod instance has its featureCompatibilityVersion (FCV) set to its MongoDB version, you cannot copy data between that instance and a mongod instance of an earlier MongoDB version.

Operations that copy data include:

db.cloneCollection() and the command cloneCollection
db.cloneDatabase() and the command clone
db.copyDatabase() and the command copydb

Example¶

To clone a database named importdb on a host named hostname, issue the following:

copy

use importdb
db.cloneDatabase("hostname")

New databases are implicitly created, so the current host does not need to have a database named importdb for this command to succeed.