What is New in NDB Cluster schema changes between existing SQL nodes. The following list describes individual enhancements relating to this integration work: To help fix this issue, schema operation timeout detection has been moved from the schema distribution client to the coordinator, providing the coordinator with an opportunity to clean up any resources used during the schema operation. The coordinator now checks ongoing schema operations for timeout at regular intervals, and marks participants that have not yet completed a given schema operation as failed when detecting timeout. It also provides suitable warnings whenever a schema operation timeout occurs. (It should be noted that, after such a timeout is detected, the schema operation itself continues.) Additional reporting is done by printing a list of active schema operations at regular intervals whenever one or more of these operations is ongoing. As an additional part of this work, a new  mysqld  option  --ndb-schema-dist-timeout  makes it possible to set the length of time to wait until a schema operation is marked as having timed out. Previously, the only  NDB  objects synchronized on connection of a new SQL node were databases and tables; MySQL NDB Cluster 8.0.14 and later also implement schema synchronization of disk data objects including tablespaces and log file groups. Among other benefits, this eliminates the possibility of a mismatch between the MySQL data dictionary and the  NDB  dictionary following a native backup and restore, in which tablespaces and log file groups were restored to the  NDB  dictionary, but not to the MySQL Server’s data dictionary. It is also no longer possible to issue a  CREATE TABLE  statement that refers to a nonexistent tablespace. Such a statement now fails with an error. As part of the schema synchronization procedure performed when starting, an SQL node now compares all databases on the cluster’s data nodes with those in its own data dictionary, and if any of these is found to be missing from the SQL node’s data dictionary, the SQL Node installs it locally by executing a  CREATE DATABASE  statement. A database thus created uses the default MySQL Server database properties (such as those as determined by  character_set_database  and collation_database ) that are in effect on this SQL node at the time the statement is executed. 3935 • NDB metadata change detection and synchronization.   NDB 8.0.16 implements a new mechanism for detection of updates to metadata for data objects such as tables, tablespaces, and log • Database DDL synchronization enhancements.   Work done in NDB 8.0.17 insures that synchronization of databases by newly joined (or rejoined) SQL nodes with those on existing SQL nodes now makes proper use of the data dictionary so that any database-level operations ( CREATE DATABASE ,  ALTER DATABASE , or  DROP DATABASE ) that may have been misssed by this SQL node are now correctly duplicated on it when it connects (or reconnects) to the cluster. • Schema synchronization of tablespace objects.   When a MySQL Server connects as an SQL node to an NDB cluster, it checks its data dictionary against the information found in the  NDB dictionary. • Disk data file distribution.   Beginning with NDB Cluster 8.0.14,  NDB  uses the MySQL data dictionary to make sure that disk data files and related constructs such as tablespaces and log file groups are correctly distributed between all connected SQL nodes. • Schema distribution enhancements.   The  NDB  schema distribution coordinator, which handles schema operations and tracks their progress, has been extended in NDB 8.0.17 to ensure that resources used during a schema operation are released at its conclusion. Previously, some of this work was done by the schema distribution client; this has been changed due to the fact that the client did not always have all needed state information, which could lead to resource leaks when the client decided to abandon the schema operation prior to completion and without informing the coordinator.