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13.1.6 ALTER LOGFILE GROUP Syntax
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.
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)
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 Syntax”):
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:
- -> FROM INFORMATION_SCHEMA.FILES
- +-------------+----------------------+----------------+
- | FILE_NAME | LOGFILE_GROUP_NUMBER | EXTRA |
- +-------------+----------------------+----------------+
- | newdata.dat | 0 | CLUSTER_NODE=3 |
- | newdata.dat | 0 | CLUSTER_NODE=4 |
- | undo_10.dat | 11 | CLUSTER_NODE=3 |
- | undo_10.dat | 11 | CLUSTER_NODE=4 |
- +-------------+----------------------+----------------+
(See Section 25.10, “The INFORMATION_SCHEMA FILES Table”.)
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.
ALTER LOGFILE GROUP
is useful only
with Disk Data storage for NDB Cluster. For more information, see
Section 22.5.13, “NDB Cluster Disk Data Tables”.
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Document créé le 26/06/2006, dernière modification le 26/10/2018
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