Defining the Data to be Collected

SNMP Data Collection


Once it has been decided for which Managed Objects (MOs) data has to be collected, you have to choose the type of data to be collected and the location. Data from the MO can be accessed from its agent.


An agent is a program running in the device which awaits data collection request. When a request is made to the agent for a particular data, the corresponding OID (Object Identifier - A unique Identification number) has to be supplied. An object identifier uniquely identifies specific characteristic of the Managed object. Hence to collect the data you have to specify the OID for that characteristic. The term OID is generically used as Data identifier. OID is SNMP-specific term.


The list of Data Identifiers can be retrieved from the MIB definition of the device. MIB is a logical database made up of the configuration, status and statistical information stored in a device. Use the MIB Browser tool bundled with WebNMS product. Load the MIB of the device from which you want to collect data. Check out the Data Identifiers for which you want to collect data.


By default, WebNMS Performance module uses SNMP for data collection and RFC1213 MIB Standards for Data Identifiers. You can plug in your own protocol and choose Data Identifiers from different MIBs.




Choosing the Data Identifier for Data Collection


In the Polling Object creation process, click the Next button to proceed. For information on the procedure so far, refer to the Selecting Devices for Data Collection topic.




For information on the Common Properties and Data Identifier (Statistics) Properties, refer to Appendix.


To add a Data Identifier (Statitics), click on the Add button, provide the required values and click on the Finish button. To modify or delete any Data Identifier, select it from the list and click Modify or Delete icon. For more details refer to the section Adding Statistics at Runtime.






Specifying Expressions using OIDs


You can form an expression using Arithmetic operators and existing Data identifiers.


Example: ( . + . ) / 2


This means an average of data collected for the instances of IfInOctets and IfOutOctets Interface. You can specify expression OID in Conf file as well as in the UI. When you do so, data is collected for all the Data Identifiers involved in the expression and resultant value is calculated based on the expression.




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