library cache lock waits

   Hello.  My application has hang couple of days ago . It looks like an alter table exchange partition with a table has been rung for about 5 hours. We have killed that command and everything went back to normal. We have reran this command later without any issues.  I'm trying to figure out what was the root of the issue. I don't see any trace files in udump directory and I don't see any errors in the alert log. In the OEM I see a very high volume of sessions waiting for library cache lock and a smaller number of