We've had an instance twice now in which a client sharepoint site collection is going into read-only mode. We have no quotas set, the health of the farm is in overall good condition, and we haven't applied unusual patches. They're a very cookie-cutter install.
We were unable to remove the read-only state in Central Administration (CA -> App Management -> Configure Quotas & Locks), and the two methods below did NOT work.
Set-SPSite -Identity <url> -Lockstate Unlock
stsadm.exe -o setsitelock -url <url> -lock none
stsadm.exe would confirm that the site was locked when using the
-o getsitelock query. The only way to remove it was a rather heavy handed server restart on the IIS/SP server, however when this happened the second time around we found that
iisreset /noforce /restart fixed it.
The logs give nothing really helpful -- even when manually executing a site collection lock on a test site I saw nothing in the logs indicating I had applied it except when I turned up the verbosity level. The question I have is: What conditions would cause a site to lock itself? What might we be missing?