content_image/829192.jpg content_image/829196.jpg content_image/829202.jpg content_image/829201.jpg
The API nodes for which no host names are set use the TCP transporter to communicate with data nodes independent of the hosts on which they are started; the parameters and values set in the [tcp default] section of the configuration file apply to all TCP transporters in the cluster. 

For optimum performance, you can define a spin time for the SHM transporter ( ShmSpinTime  parameter); this affects both the data node receiver thread and the poll owner (receive thread or user thread) in NDB . 

• Checksum 

<img src='content_image/829192.jpg'>

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. 

• Group 

<img src='content_image/829196.jpg'>

Determines the group proximity; a smaller value is interpreted as being closer. The default value is sufficient for most conditions. 

• HostName1 

<img src='content_image/829202.jpg'>

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 host names or IP addresses. 

• HostName2 

<img src='content_image/829201.jpg'>

