CREATE LOGFILE GROUPlogfile_group
ADD UNDOFILE 'undo_file
' [INITIAL_SIZE [=]initial_size
] [UNDO_BUFFER_SIZE [=]undo_buffer_size
] [REDO_BUFFER_SIZE [=]redo_buffer_size
] [NODEGROUP [=]nodegroup_id
] [WAIT] [COMMENT [=]comment_text
] 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 8.2, “Schema Object Names”.
All MySQL 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.
Beginning with MySQL 5.1.8, you can have only one log file group per Cluster at any given time. (See Bug#16386)
Prior to MySQL Cluster NDB 6.2.17, 6.3.23, and 6.4.3, path and file names for undo log files could not be longer than 128 characters. (Bug#31769)
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).
Beginning with MySQL Cluster NDB 6.2.17, 6.3.23, and 6.4.3, the
maximum permitted for UNDO_BUFFER_SIZE
is
600M
; previously, it was
150M
. (Bug#34102)
On 32-bit systems, the maximum supported value for
INITIAL_SIZE
is 4G
.
(Bug#29186)
Beginning with MySQL Cluster NDB 2.1.18, 6.3.24, and 7.0.4, the
minimum allowed value for INITIAL_SIZE
is
1M
. (Bug#29574)
The ENGINE
parameter determines the storage
engine to be used by this log file group, with
engine_name
being the name of the
storage engine. In MySQL 5.1.
engine_name
must be one of the values
NDB
or
NDBCLUSTER
.
REDO_BUFFER_SIZE
,
NODEGROUP
, WAIT
, and
COMMENT
are parsed but ignored, and so have no
effect in MySQL 5.1. These options are intended for
future expansion.
When used with ENGINE [=] NDB
, a log file group
and associated UNDO
log file are created on
each 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 LOGFILE_GROUP_NAME, LOGFILE_GROUP_NUMBER, EXTRA
->FROM INFORMATION_SCHEMA.FILES
->WHERE FILE_NAME = 'undo_10.dat';
+--------------------+----------------------+----------------+ | LOGFILE_GROUP_NAME | LOGFILE_GROUP_NUMBER | EXTRA | +--------------------+----------------------+----------------+ | lg_3 | 11 | CLUSTER_NODE=3 | | lg_3 | 11 | CLUSTER_NODE=4 | +--------------------+----------------------+----------------+ 2 rows in set (0.06 sec)
CREATE LOGFILE GROUP
was added in MySQL 5.1.6.
In MySQL 5.1, it is useful only with Disk Data storage for MySQL
Cluster. See Section 17.5.10, “MySQL Cluster Disk Data Tables”.
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