content_image/861910.jpg content_image/861921.jpg
[NODEGROUP [=] nodegroup_id ] [WAIT] [COMMENT [=] ’ string ’] ENGINE [=] engine_name 

This statement creates a new log file group named logfile_group  having a single UNDO  file named ’ undo_file ’. A CREATE LOGFILE GROUP  statement has one and only one ADD UNDOFILE  clause. For rules covering the naming of log file groups, see Section 9.2, “Schema Object Names” . 

<img src='content_image/861910.jpg'>

There can be only one log file group per NDB Cluster instance at any given time. 

## Note 

All NDB Cluster Disk Data objects share the same namespace. This means that each Disk Data object  must be uniquely named (and not merely each Disk Data object of a given type). For example, you cannot have a tablespace and a log file group with the same name, or a tablespace and a data file with the same name. 

The optional INITIAL_SIZE  parameter sets the UNDO  file’s initial size; if not specified, it defaults to 128M (128 megabytes). The optional UNDO_BUFFER_SIZE  parameter sets the size used by the UNDO  buffer for the log file group; The default value for UNDO_BUFFER_SIZE  is 8M  (eight megabytes); this value cannot exceed the amount of system memory available. Both of these parameters are specified in bytes. You may optionally follow either or both of these with a one-letter abbreviation for an order of magnitude, similar to those used in my.cnf . Generally, this is one of the letters M  (for megabytes) or G  (for gigabytes). 

Memory used for UNDO_BUFFER_SIZE  comes from the global pool whose size is determined by the value of the SharedGlobalMemory  data node configuration parameter. This includes any default value implied for this option by the setting of the InitialLogFileGroup  data node configuration parameter. 

The maximum permitted for UNDO_BUFFER_SIZE  is 629145600 (600 MB). 

On 32-bit systems, the maximum supported value for INITIAL_SIZE  is 4294967296 (4 GB). (Bug #29186) 

The minimum allowed value for INITIAL_SIZE  is 1048576 (1 MB). 

The ENGINE  option determines the storage engine to be used by this log file group, with engine_name being the name of the storage engine. In MySQL 8.0, this must be NDB  (or NDBCLUSTER ). If ENGINE  is not set, MySQL tries to use the engine specified by the default_storage_engine  server system variable (formerly storage_engine ). In any case, if the engine is not specified as NDB  or NDBCLUSTER , the CREATE LOGFILE GROUP  statement appears to succeed but actually fails to create the log file group, as shown here: 

mysql> CREATE LOGFILE GROUP lg1 -> ADD UNDOFILE ’undo.dat’ INITIAL_SIZE = 10M; Query OK, 0 rows affected, 1 warning (0.00 sec) mysql> SHOW WARNINGS; 

<img src='content_image/861921.jpg'>

mysql> DROP LOGFILE GROUP lg1 ENGINE = NDB; ERROR 1529 (HY000): Failed to drop LOGFILE GROUP mysql> CREATE LOGFILE GROUP lg1 -> ADD UNDOFILE ’undo.dat’ INITIAL_SIZE = 10M 

