How to improve MultiTech rCell modem performance (SMS)

How to improve MultiTech rCell modem performance (SMS)

This article provides information for users experiencing performance issues with the MultiTech rCell modem used for TopView SMS notification.

Symptoms
  1. The user cannot log into the modem web UI 
  2. When logging into the modem web UI, the screens are slow to update or timeouts occur 
  3. TopView periodically fails to send or receive SMS messages due to a timeout error
  4. Performance monitoring using the modem's performance tools shows high CPU usage
Background
TopView uses a REST API from MultiTech to query information about the modem and to send/receive SMS messages.
Some of these calls require more modem resources than others. Specifically, calls that check the modem's SMS inbox and outbox require significant modem resources if there are a large number of messages in the inbox/outbox.
When TopView sends an SMS message through the modem, the call returns "successful" but the SMS message has not yet been sent by the modem. It is put into a queue, and the messages in the queue are then sent.
As part of TopView's Engine Health Monitoring, the Engine will query the modem's SMS outbox to see if the last SMS send failed.  The API does not allow us to query information about the most recent sent message. Instead, we must query for the entire SMS outbox.
The default max size of the SMS outbox is 1000 (the modem will store the details of the last sent 1000 SMS messages). Therefore, when TopView Engine Health checks the success/failure of the last sent message, it queries and returns up to 1000 messages. This call can require significant modem resources when called frequently.

How to improve modem performance
  1. Upgrade to TopView 7.2 or later
    1. Version 7.2 contains significant improvements in how we call into the modem along with new options for how frequently Engine Health will check for failed SMS messages. There are also new recommended settings for the modem inbox/outbox max size.  
      1. See the 7.2 release notes for more information
  2. TopView 7.1 and earlier
    1. If you cannot upgrade to v7.2 or later, reducing the size of the modem's SMS inbox and outbox can significantly improve modem performance.
    2. Log into the modem web UI
      1. SMS > SMS Configuration
      2. Sent SMS to keep: 99
      3. Received SMS to keep: 99
      4. Click [Submit] to save these settings
      5. Click [Save and Apply] to apply the settings