MongoDB Documentation, Release 3.0.4 • diagLogging • eval , db.eval() • db.collection.copyTo() In addition, you cannot use the now deprecated eval command or the db.eval() method to invoke mapReduce or db.collection.mapReduce() . Date and Timestamp Comparison Order MongoDB 3.0 no longer treats the Timestamp (page 180) and the Date (page 180) data types as equivalent for comparison purposes. Instead, the Timestamp (page 180) data type has a higher comparison/sort order (i.e. is “greater”) than the Date (page 180) data type. If your application relies on the equivalent comparison/sort order of Date and Timestamp objects, modify your application accordingly before upgrading. Server Status Output Change The serverStatus command and the db.serverStatus() method no longer return workingSet , indexCounters , and recordStats sections in the output. Unix Socket Permissions Change Unix domain socket file permission now defaults to 0700 . To change the permission, MongoDB provides the net.unixDomainSocket.filePermissions setting as well as the --filePermission option. Some changes in 3.0 can affect compatibility (page 804) and may require user actions. For a detailed list of compati- bility changes, see Compatibility Changes in MongoDB 3.0 (page 804). Upgrade MongoDB to 3.0 In the general case, the upgrade from MongoDB 2.6 to 3.0 is a binary-compatible “drop- in” upgrade: shut down the mongod instances and replace them with mongod instances running 3.0. However , before you attempt any upgrade please familiarize yourself with the content of this document, particularly the procedure for upgrading sharded clusters (page 813). Upgrade Process If you need guidance on upgrading to 3.0, MongoDB offers consulting 254 to help ensure a smooth transition without interruption to your MongoDB application. Upgrade Requirements To upgrade an existing MongoDB deployment to 3.0, you must be running 2.6. If you’re running a version of MongoDB before 2.6, you must upgrade to 2.6 before upgrading to 3.0. See Upgrade MongoDB to 2.6 (page 866) for the procedure to upgrade from 2.4 to 2.6. Once upgraded to MongoDB 2.6, you cannot downgrade to any version earlier than MongoDB 2.4. If your existing MongoDB deployment is already running with authentication and authorization, your user data model authSchema must be at least version 3. To verify the version of your existing authSchema , see MongoDB 2.4 User Model Removed (page 807). To upgrade your authSchema version, see Upgrade User Authorization Data to 2.6 Format (page 870) for details. Preparedness Before upgrading MongoDB, always test your application in a staging environment before deploying the upgrade to your production environment. Some changes in MongoDB 3.0 require manual checks and intervention. Before beginning your upgrade, see the Compatibility Changes in MongoDB 3.0 (page 804) document to ensure that your applications and deployments are compatible with MongoDB 3.0. Resolve the incompatibilities in your deployment before starting the upgrade. $^{254}$https://www.mongodb.com/products/consulting?jmp=docs#major_version_upgrade 810 Chapter 12. Release Notes Upgrade Recommendations and Checklists When upgrading, consider the following: