Problem

We do lock on the whole TM as we can't lock records.

This may cause inability to acquire read lock (for searches) if someone already got write lock (for update in maintenance) and this results in really poor UX.

Solution

We have to wait a bit to non-blocking acquire of lock. Maybe ~20 sec or so.

This will allow user to get shared lock if someone doing relatively fast mutations (like update) and still get an error if TM is really busy (like import or reorganise)