Oracle 5.0, Reference Manual

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MySQL Cluster Configuration Files
1567
Effective Version Type/Units Default Range/Values
MySQL 5.0.0 integer 40 20 - 4G
Restart Type: N
This parameter sets a ceiling on how many internal threads to allocate for open files. Any situation
requiring a change in this parameter should be reported as a bug.
The default value is 40.
•
MaxNoOfSavedMessages
Effective Version Type/Units Default Range/Values
MySQL 5.0.0 integer 25 0 - 4G
Restart Type: N
This parameter sets the maximum number of trace files that are kept before overwriting old ones.
Trace files are generated when, for whatever reason, the node crashes.
The default is 25 trace files.
Metadata objects. The next set of
[ndbd]
parameters defines pool sizes for metadata objects,
used to define the maximum number of attributes, tables, indexes, and trigger objects used by indexes,
events, and replication between clusters. Note that these act merely as “suggestions” to the cluster,
and any that are not specified revert to the default values shown.
•
MaxNoOfAttributes
Effective Version Type/Units Default Range/Values
MySQL 5.0.0 integer 1000 32 - 4G
Restart Type: N
This parameter sets a suggested maximum number of attributes that can be defined in the cluster;
like
MaxNoOfTables
[1568] , it is not intended to function as a hard upper limit.
A known issue in MySQL Cluster in MySQL 5.0 is that this parameter is occasionally treated as a
hard limit for certain operations. This can lead to confusion when it is sometimes possible (or not
possible, depending on the circumstances) to create more than
MaxNoOfAttributes
attributes.
This is fixed in MySQL Cluster NDB 6.3 and later. (Bug #61684)
The default value is 1000, with the minimum possible value being 32. The maximum is 4294967039.
Each attribute consumes around 200 bytes of storage per node due to the fact that all metadata is
fully replicated on the servers.
When setting
MaxNoOfAttributes
, it is important to prepare in advance for any
ALTER
TABLE
statements that you might want to perform in the future. This is due to the fact, during the
execution of
ALTER TABLE
on a Cluster table, 3 times the number of attributes as in the original
table are used, and a good practice is to permit double this amount. For example, if the MySQL
Cluster table having the greatest number of attributes (
greatest_number_of_attributes
)
has 100 attributes, a good starting point for the value of
MaxNoOfAttributes
would be
6 *
greatest_number_of_attributes = 600
.
You should also estimate the average number of attributes per table and multiply this by the total
number of MySQL Cluster tables. If this value is larger than the value obtained in the previous
paragraph, you should use the larger value instead.