Ask HN: Best way to deal with multitasking / context switching?

I am the "database guy" for a sequencing centre. I have built the database and web front end from scratch, and the organization has grown over the last 3 years since I started there.

There are a number of major improvement that could be made to the system, but as it is live, I find I am unable to work on anything that takes more than a couple of days coding, as I am always interrupted by trivial but "urgent" things that need fixed. (Most of the time it is user input errors - they insist on using excel for uploading data, despite it being a very error prone process).

Does anyone have advice for working on something that requires more effort, while there are constant interruptions?