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ADD UNDOFILE ’ file_name ’ [INITIAL_SIZE [=] size ] [WAIT] ENGINE [=] engine_name 

This statement adds an UNDO  file named ’ file_name ’ to an existing log file group logfile_group . An ALTER LOGFILE GROUP  statement has one and only one ADD UNDOFILE  clause. No DROP UNDOFILE clause is currently supported. 

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## 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 an undo log file with the same name, or an undo log file and a data file with the same name. 

The optional INITIAL_SIZE  parameter sets the UNDO  file’s initial size in bytes; if not specified, the initial size defaults to 134217728 (128 MB). You may optionally follow size  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  (megabytes) or G  (gigabytes). (Bug #13116514, Bug #16104705, Bug #62858) 

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). (Bug #29574) 

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## Note 

WAIT  is parsed but otherwise ignored. This keyword currently has no effect, and is intended for future expansion. 

The ENGINE  parameter (required) determines the storage engine which is used by this log file group, with engine_name  being the name of the storage engine. Currently, the only accepted values for engine_name  are “ NDBCLUSTER ”  and “ NDB ” . The two values are equivalent. 

Here is an example, which assumes that the log file group lg_3  has already been created using CREATE LOGFILE GROUP  (see Section 13.1.16, “CREATE LOGFILE GROUP Statement” ): 

ALTER LOGFILE GROUP lg_3 ADD UNDOFILE ’undo_10.dat’ INITIAL_SIZE=32M ENGINE=NDBCLUSTER; 

When ALTER LOGFILE GROUP  is used with ENGINE = NDBCLUSTER  (alternatively, ENGINE = NDB ), an UNDO  log file is created on each NDB Cluster data node. You can verify that the UNDO  files were created and obtain information about them by querying the INFORMATION_SCHEMA.FILES  table. For example: 

mysql> SELECT FILE_NAME, LOGFILE_GROUP_NUMBER, EXTRA -> FROM INFORMATION_SCHEMA.FILES -> WHERE LOGFILE_GROUP_NAME = ’lg_3’; 

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(See Section 26.3.15, “The INFORMATION_SCHEMA FILES Table” .) 

