Data Access Settings

Access

The most important entry in an object-type description is the ACCESS line. This controls whether you can read and write the data described in the object-type.

There are three access settings: not-accessible, read-only and read-write.

Not-accessible means the object-type is there, but you can't request the data in a GetRequest.

Read-only means you can request the data in a GetRequest, but you can't write new data for the object-type in a SetRequest.

Read-write means you're free to retrieve the data in a GetRequest and write new data for the object-type in a SetRequest.

In the example of the alarm state object-type:

tmonAState OBJECT-TYPE
SYNTAX DisplayString (SIZE (8))
ACCESS read-only
STATUS mandatory
DESCRIPTION "The current alarm state."
::= {tmonAlarmEntry 4}

The access here is read-only, because the alarm state is set by the alarm input on that alarm point.

Here's an example of an object-type with read-write access:

psRTUDateTime OBJECT-TYPE
SYNTAX DisplayString (SIZE (23))
ACCESS read-write
STATUS mandatory
DESCRIPTION "The RTU system date and time."
::= {dpsRTUIdent 4}

Here the access is read-write, because this is a value that you can set from your SNMP manager. You can retrieve the current settings from the RTU's internal clock through a GetRequest. And if the clock needs to be reset, you can write new data in a SetRequest.

I want to use a device feature that isn't described in the MIB. What can I do?

You can ask the vendor to extend the MIB to include this feature. DPS Telecom has extended its MIB to support client needs and will continue to do so if a client needs it.

But you need to understand that extending a MIB is actually a software development project. The MIB is not just a text file. It's also a software interface document to the embedded firmware of your SNMP device. Making additions to the MIB requires rewriting the device firmware.

This is a serious project, involving writing code, debugging it, and undergoing a thorough quality assurance process. Extending a MIB is a large commitment of time and resources.