MongoDB Documentation  Release 3.0.4 The method returns a WriteResult object with the status of the operation. Upon successful update  the WriteResult object should have "nModified" equal to 1 . The method returns a WriteResult object with the number of documents removed in the "nRemoved" field. Note: The cluster’s mongos instances will fail to detect the authorization model downgrade until the user cache is refreshed. You can run invalidateUserCache on each mongos instance to refresh immediately  or you can wait until the cache is refreshed automatically at the end of the user cache invalidation interval . To run invalidateUserCache   you must have privilege with invalidateUserCache (page 421) action  which is granted by userAdminAnyDatabase (page 412) and hostManager (page 410) roles. For a sharded cluster  repeat the downgrade process by connecting to the primary replica set member for each shard. Result The downgrade process returns the user data to its state prior to upgrading to 2.6 authorization model. Any changes made to the user/role data using the 2.6 users model will be lost. Text Index Version Check If you have version 2 text indexes (i.e. the default version for text indexes in MongoDB 2.6)  drop the version 2 text indexes before downgrading MongoDB. After the downgrade  enable text search and recreate the dropped text indexes. To determine the version of your text indexes  run db.collection.getIndexes() to view index specifica- tions. For text indexes  the method returns the version information in the field textIndexVersion . For example  the following shows that the text index on the quotes collection is version 2. Chapter 12. Release Notes 874 Downgrade Updated Indexes Step 4: Remove existing documents from the admin.system.users collection. Step 6: Update the version document for the authSchema . Step 5: Copy documents from the admin.system.backup_users collection. Copy all documents from the admin.system.backup_users   created during the 2.6 upgrade  to admin.system.users . db.getSiblingDB("admin").system.backup_users.find().forEach( function (userDoc) { status = db.getSiblingDB("admin").system.users.insert( userDoc ); if (status.hasWriteError()) { print(status.writeError); } } ); db.getSiblingDB("admin").system.version.update( { _id: "authSchema" }  { $set: { currentVersion: 1 } } ) { "v" : 1  "key" : { "_fts" : "text"  "_ftsx" : 1 db.getSiblingDB("admin").system.users.remove( {} )