Spec-Zone .ru
спецификации, руководства, описания, API
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Spec-Zone .ru
спецификации, руководства, описания, API
|
MySQL Cluster attempts to use the shared memory transporter and configure it automatically where possible. [shm] sections in the config.ini file explicitly define
shared-memory connections between nodes in the cluster. When explicitly defining shared memory as the connection
method, it is necessary to define at least NodeId1, NodeId2, and ShmKey. All other parameters have default values that should work well in
most cases.
SHM functionality is considered experimental only. It is not officially supported in any current MySQL Cluster release, and testing results indicate that SHM performance is not appreciably greater than when using TCP/IP for the transporter.
For these reasons, you must determine for yourself or by using our free resources (forums, mailing lists) whether SHM can be made to work correctly in your specific case.
To identify a connection between two nodes it is necessary to provide node identifiers for each of
them, as NodeId1 and NodeId2.
| Effective Version | Type/Units | Default | Range/Values |
|---|---|---|---|
| NDB 7.3.0 | name or IP address | [none] | ... |
| Restart Type: N | |||
| Effective Version | Type/Units | Default | Range/Values |
|---|---|---|---|
| NDB 7.3.0 | name or IP address | [none] | ... |
| Restart Type: N | |||
The HostName1 and HostName2 parameters can
be used to specify specific network interfaces to be used for a given SHM connection between two
nodes. The values used for these parameters can be hostnames or IP addresses.
When setting up shared memory segments, a node ID, expressed as an integer, is used to identify uniquely the shared memory segment to use for the communication. There is no default value.
Each SHM connection has a shared memory segment where messages between nodes are placed by the
sender and read by the reader. The size of this segment is defined by ShmSize. The default value is 1MB.
| Effective Version | Type/Units | Default | Range/Values |
|---|---|---|---|
| NDB 7.3.0 | boolean | false | true, false |
| Restart Type: N | |||
To retrace the path of a distributed message, it is necessary to provide each message with a unique
identifier. Setting this parameter to Y causes these message IDs to be
transported over the network as well. This feature is disabled by default in production builds, and
enabled in -debug builds.
| Effective Version | Type/Units | Default | Range/Values |
|---|---|---|---|
| NDB 7.3.0 | boolean | true | true, false |
| Restart Type: N | |||
This parameter is a boolean (Y/N)
parameter which is disabled by default. When it is enabled, checksums for all messages are
calculated before being placed in the send buffer.
This feature prevents messages from being corrupted while waiting in the send buffer. It also serves as a check against data being corrupted during transport.
When using the shared memory transporter, a process sends an operating system signal to the other process when there is new data available in the shared memory. Should that signal conflict with with an existing signal, this parameter can be used to change it. This is a possibility when using SHM due to the fact that different operating systems use different signal numbers.
The default value of SigNum is 0; therefore, it must be set to avoid errors in the cluster
log when using the shared memory transporter. Typically, this parameter is set to 10 in the [shm default] section of the config.ini
file.