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Before you attempt any downgrade, familiarize yourself with the content of this document.
Once upgraded to 3.6, if you need to downgrade, we recommend downgrading to the latest patch release of 3.4.
Optional but Recommended. Create a backup of your database.
Before downgrading the binaries, you must downgrade the feature compatibility version and remove any 3.6 features incompatible with 3.4 versions as outlined below. These steps are necessary only if featureCompatibilityVersion has ever been set to "3.6".
mongo shell to the mongod instance.featureCompatibilityVersion to "3.4".
The setFeatureCompatibilityVersion command performs writes to an internal system collection and is idempotent. If for any reason the command does not complete successfully, retry the command on the mongod instance.
Remove all persisted features that are incompatible with 3.4. For example, if you have defined any any view definitions, document validators, and partial index filters that use 3.6 query features such as $jsonSchema or $expr, you must remove them.
Using either a package manager or a manual download, get the latest release in the 3.4 series. If using a package manager, add a new repository for the 3.4 binaries, then perform the actual downgrade process.
Once upgraded to 3.6, if you need to downgrade, we recommend downgrading to the latest patch release of 3.4.
mongod instance.¶Shut down your mongod instance. Replace the existing binary with the downloaded mongod binary and restart.
mongod process.
Note
If you do not perform a clean shut down, errors may result that prevent the mongod process from starting.
Forcibly terminating the mongod process may cause inaccurate results for db.collection.count() and db.stats() as well as lengthen startup time the next time that the mongod process is restarted.
This applies whether you attempt to terminate the mongod process from the command line via kill or similar, or whether you use your platform’s initialization system to issue a stop command, like sudo systemctl stop mongod or sudo service mongod stop.
mongod process.