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Communication Library Parameters

Updated at: Jul 14, 2021 GMT+08:00

This section describes parameter settings and value ranges for communication libraries.

comm_control_port

Parameter description: Specifies the TCP listening port used by the TCP proxy communication library or SCTP communication library, respectively.

Type: POSTMASTER

Value range: an integer ranging from 0 to 65535

Default value: port + Number of primary DNs on the local host x 2 + Sequence number of the local DN on the local host + 1

This port number is automatically allocated during cluster deployment. Do not change the parameter setting. If the port number is incorrectly set, the database communication fails.

comm_max_datanode

Parameter description: Specifies the maximum number of DNs supported by the TCP proxy communication library or SCTP communication library.

Type: USERSET

Value range: an integer ranging from 1 to 8192

Default value: If the number of DNs is greater than 256, the default value is greater than or equal to the Nth power of 2 of the number of primary DNs. If the number of DNs is less than or equal to 256, set this parameter to 256.

comm_quota_size

Parameter description: Specifies the maximum size of packets that can be consecutively sent by the TCP proxy communication library or SCTP communication library. When you use a 1GE NIC, a small value ranging from 20 KB to 40 KB is recommended.

Type: USERSET

Value range: an integer ranging from 0 to 102400. The default unit is KB. The value 0 indicates that the quota mechanism is not used.

Default value: 1 MB

comm_no_delay

Parameter description: Specifies whether to use the NO_DELAY attribute of the communication library connection. Restart the cluster for the setting to take effect.

Type: USERSET

Value range: Boolean

Default value: off

If packet loss occurs because a large number of packets are received per second, set this parameter to off to reduce the total number of packets.

comm_debug_mode

Parameter description: Specifies the debug mode of the TCP proxy communication library or SCTP communication library, that is, whether to print logs about the communication layer. The setting is effective at the session layer.

When the switch is set to on, the number of printed logs is huge, adding extra overhead and reducing database performance. Therefore, set the switch to on only in the debug mode.

Type: USERSET

Value range: Boolean

  • on indicates the detailed debug log of the communication library is printed.
  • off indicates the detailed debug log of the communication library is not printed.

Default value: off

comm_ackchk_time

Parameter description: Specifies the duration after which the communication library server automatically triggers ACK when no data package is received.

Type: USERSET

Value range: an integer ranging from 0 to 20000. The unit is millisecond (ms). 0 indicates that automatic ACK triggering is disabled.

Default value: 2000

comm_timer_mode

Parameter description: Specifies the timer mode of the TCP proxy communication library or SCTP communication library, that is, whether to print timer logs in each phase of the communication layer. The setting is effective at the session layer.

When the switch is set to on, the number of printed logs is huge, adding extra overhead and reducing database performance. Therefore, set the switch to on only in the debug mode.

Type: USERSET

Value range: Boolean

  • on indicates the detailed timer log of the communication library is printed.
  • off indicates the detailed timer log of the communication library is not printed.

Default value: off

comm_stat_mode

Parameter description: Specifies the statistics mode of the TCP proxy communication library or SCTP communication library, that is, whether to print statistics about the communication layer. The setting is effective at the session layer.

When the switch is set to on, the number of printed logs is huge, adding extra overhead and reducing database performance. Therefore, set the switch to on only in the debug mode.

Type: USERSET

Value range: Boolean

  • on indicates the statistics log of the communication library is printed.
  • off indicates the statistics log of the communication library is not printed.

Default value: off

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