Oracle 5.0 Reference Manual page 1583

It is a good idea to adjust the value of this parameter according to the size and number of
transactions. When performing transactions of only a few operations each and not involving a great
many records, there is no need to set this parameter very high. When performing large transactions
involving many records need to set this parameter higher.
Records are kept for each transaction updating cluster data, both in the transaction coordinator
and in the nodes where the actual updates are performed. These records contain state information
needed to find UNDO records for rollback, lock queues, and other purposes.
This parameter should be set to the number of records to be updated simultaneously in transactions,
divided by the number of cluster data nodes. For example, in a cluster which has four data nodes
and which is expected to handle one million concurrent updates using transactions, you should set
this value to 1000000 / 4 = 250000. To help provide resiliency against failures, it is suggested that
you set this parameter to a value that is high enough to permit an individual data node to handle
the load for its node group. In other words, you should set the value equal to
concurrent operations / number of node
node group, this is the same as the total number of concurrent operations for the entire cluster.)
Because each transaction always involves at least one operation, the value of
MaxNoOfConcurrentOperations
MaxNoOfConcurrentTransactions
Read queries which set locks also cause operation records to be created. Some extra space is
allocated within individual nodes to accommodate cases where the distribution is not perfect over the
nodes.
When queries make use of the unique hash index, there are actually two operation records used
per record in the transaction. The first record represents the read in the index table and the second
handles the operation on the base table.
The default value is 32768.
This parameter actually handles two values that can be configured separately. The first of these
specifies how many operation records are to be placed with the transaction coordinator. The second
part specifies how many operation records are to be local to the database.
A very large transaction performed on an eight-node cluster requires as many operation records
in the transaction coordinator as there are reads, updates, and deletes involved in the transaction.
However, the operation records of the are spread over all eight nodes. Thus, if it is necessary to
configure the system for one very large transaction, it is a good idea to configure the two parts
separately.
MaxNoOfConcurrentOperations
operation records in the transaction coordinator portion of the node.
It is also important to have an idea of the memory requirements for operation records. These
consume about 1KB per record.
•
MaxNoOfLocalOperations
Effective Version
MySQL 5.0.0
Restart Type: N
By default, this parameter is calculated as 1.1 × MaxNoOfConcurrentOperations. This fits
systems with many simultaneous transactions, none of them being very large. If there is a need to
handle one very large transaction at a time and there are many nodes, it is a good idea to override
the default value by explicitly specifying this parameter.
MySQL Cluster Configuration Files
should always be greater than or equal to the value of
[1562].
Type/Units
integer
1563
groups. (In the case where there is a single
will always be used to calculate the number of
Default
UNDEFINED
total number of
Range/Values
32 - 4G