OkiePC
Lifetime Supporting Member
I would have a chat with Redlion:
https://www.redlion.net/family/data-acquisition
They can collect data and then upload to an SQL database once a connection is available. They have a NetworkPing(address, timeout) function that allows you to periodically check for an Internet connection.
Red Lions are great at this as long as it is a Microsoft SQL server. Their connector is specific and limited to the "TDS" (tabular data stream) protocol. I'm not a database guy, so I am not sure if there are other SQL server products that support it, but I do know that you can't make a Red Lion connect with MySQL, for example. Crimson gives you a lot of settings and features to deal with intermittent updates.
https://support.redlion.net/hc/en-us/articles/360016743131-Crimson-3-x-SQL-Synchronization