Recently we encountered an odd problem. Many foreground sessions are waiting for background process w000 and w008.
This background process coordinates the execution of various space management tasks, including proactive space allocation and space reclamation. SMCO dynamically spawns slave processes (Wnnn) to implement these tasks.
top shows that the process status is D (uninterruptible sleep) and kill -9 pid would not work. In addition, strace pid xxx doesn’t give any feedback.
‘shutdown immediate’ would not work and after killing smon process, ipcrm -m could not clean shared memory.
In the end, we powered off the host and the database reverted to normal. We still could not figure out what exactly happened.
DB: Oracle 18.104.22.168
OS: Redhat Linux 6.0 x86_64