Symptoms
OS hang, sometimes with open file errors in journals
Customer application degrades with errors "unable to open file", "too many open files"
Hangs and third-party (compatibility) issues often require advanced data collection and are sophisticated to investigate. However, a quick check is possible:
On a system where KESL has worked for some time (not immediately after reboot/restart), validate the output of the following command, ran as root, for numerous records of /u