database mysterious slowdown

Every once in a while we see a short period where all three sites of the IVR fail on their calls to database get account info.  The most recent cases were yesterday in the following periods: 2014-05-05 13:58:45 - 13:59:25 CT 2014-05-05 14:28:48 - 14:29:32 CT "fail" means that a simple account lookup, which usually takes less than 1 second, takes more than 15 seconds (the IVR gives up and times out if it waits for more than 15 seconds for database to respond). We guess it is database blocking which cause this. Is any way we can do the