we have one receive location of type SQL in our Biztalk Application on productin server and it got disabled after some days and logged an error in event log like that "Threshol on Receive Location"
it was very annoying for us to enable it manually and we were not be able to find the root cause of this problem, then after some R&D i have come to know that
Biztalk keeps polling sql server after every x milliseconds. In some cases its configurable. For some adapters its not.
we have error threshold value set to 5 , mean after 5 continous error from sql server the receive location would be disable as Microsoft says about Error Trhreshold :
The Error Threshold is used to specify the maximum number of continuous errors received before disabling the receive handler.
so when for some maintaine work or with due ot any other reason if sql server is down and Biztalk got 5 continous error from sql server then it disabled the receive location and put some error in log related to threshold.
so what we did just change the value of ErrorThreshold from 5 to 500 and restart the host instance then we did not face this issue again.