# What does "Concurrent spin time" mean in the Gurobi log and what does choosing Method=3 do?

We are using Gurobi 9.0.2 to solve complex mixed integer linear programs for which we are attempting to maintain total unimodularity (TUM). In our log file we see things like this:

Concurrent spin time: 13403.45s (can be avoided by choosing Method=3)
Concurrent spin time: 921.14s (can be avoided by choosing Method=3)
Concurrent spin time: 244.37s (can be avoided by choosing Method=3)


What does Concurrent spin time mean and what does Method=3 do?