Clarification of the modbus_db size in RUTxxx devices


I’d like to clarify which is the correct information for the maximum modbus_db file size. My current modbus_db file size is 1.3MB with nearly 13,000 rows and each row contains the response from each Modbus read request (smallest request is 1 register and largest is 24 registers).

I am testing using the RUT200 running RUT2M_R_00.07.06 firmware and using Modbus TCP to read 67 different 16bit registers across 8 requests every 60 seconds. I then use MQTT to transfer the data to Azure IoT Hub with the Data To Server functionality. This configuration adds data to the modbus_db providing temporary short term local storage.

I’m trying to determine how many readings thr modbus_db file will hold but there seems to be inconsistent information about this.

This post suggests a size limit of 1.2MB.

This post suggests a size limit of 22.5MB.
65303 - local storage for modbus data logging

This post suggests a row limit of 20,000.

Which is correct, or are they al correct due to the size of each Modbus read?

Many thanks,


Hello Alan,

Yes, both are correct, the size limit for modbus database is 1.2MB. to avoid allocating more memory required by the device itself for other processes.

Teltonika devices can store up to 20,000 modbus records, so it really depends on the size of the modbus records itself. Once the 20,000 has been reached, it will just overwrite to oldest data, keeping it at the mentioned limit.

Therefore, you can have 20,000 records existing on the db, but due to the smaller size and/or data type, the size of the database may not even reach the mentioned size limit (1.2 MB).

Best regards,

Hi Rob,

Many thanks for your prompt response and clarification.

Modbus db can hold up to 20,000 records or 1.2MB whichever is reached first.

That will alow me to determine the time period coverd by local storage.



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