Advanced SNMP Table Polling Settings (Driver)

The Advanced SNMP Table Polling property enables SNMP table polling results to be filtered by row and column, as well as set maximums for the number of rows or columns to be retrieved per protocol data unit (PDU). Both columns and rows can be filtered by using an expression to exclude certain columns or rows.

Each device has an Advanced SNMP Table Polling settings which only apply to that individual device. When a new device is created, it will copy all Advanced SNMP Table Polling settings from the driver settings. Settings for each individual device can then be customized in the device configuration page.

The properties Maximum Columns per PDU and Maximum Rows per PDU should be set to reflect the actual size of the table.

If the table size is unknown, the table can be walked iteratively by setting these properties to -1, however, this should be avoided because it can result in degraded performance.

Automatic Optimization of SNMP Polling Configuration

When Enable Automatic SNMP Table Configurations and Enable SNMP Table Error Processing properties are both activated, the driver will attempt to identify the optimal number of rows and columns to read per PDU. The current configuration values used during optimization are displayed for each variable in the SNMP Table Read Status. The optimization algorithm updates configuration values under the following conditions:

  • After each successful read operation using configurations which were already successful, the driver will increment the number of rows and columns to read per PDU. The maximum optimized configuration cannot exceed the values set for Maximum Columns per PDU and Maximum Rows per PDU.

  • After any read operation which produced errors, the number of rows and columns to read per PDU is decremented.

Polling Settings Parameters

The following table describes the parameters available for configuring SNMP polling settings.

Field

Description

Variable Name

The name of the Data Table that is returned by the SNMP polling result. At the device level, the variable names are automatically imported when the device receives a poll response.

Columns Polling Rules

Data table which defines which columns will be excluded from the incoming data set. At the device level, the list of columns returned by the variable during poll response is automatically populated.

Field Name

Field Type

Notes

Column Name (fieldName)

String

Name of the column.

Exclude Column (fieldExclude)

Boolean

If TRUE, the column will be excluded.

Column Condition Expression (fieldExpression)

String

Expression with Boolean return value. Column will be excluded in the case that the expression returns FALSE.

Column Condition Expression Resolution Environment

Default Context

Current device context.

Default Data Table

List of field names returned by the variable.

Default Row

0

Environment Variables

Standard variables only.

Row Polling Expression

Expression with Boolean return value. The expression runs against each row of the variable. If the expression result is FALSE, the row is excluded.

Row Condition Expression Resolution Environment

Default Context

Current device context.

Default Data Table

Current row of the variable data table

Default Row

0

Environment Variables

Standard variables only.

Maximum Columns per PDU

Advanced setting field, indicates the maximum number of columns to retrieve per protocol data unit (PDU) for the indicated variable.

Maximum Rows per PDU

Advanced setting field, indicates the maximum number of rows to retrieve per protocol data unit (PDU) for the indicated variable.

Enable SNMP Table Error Processing

Allows the error processing logic for SNMP tables to adjust read settings in the event of errors, in order to successfully read the table.

Enable Automatic SNMP Table Configurations

Allows the driver to attempt to automatically adjust SNMP table configurations in order to optimize performance.

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