Oracle processes use semaphores for inter-process locking. If the system runs out of available semaphores (e.g., too many Oracle instances or processes), the OS returns EAGAIN .
By methodically checking process counts, kernel parameters, and user limits, you can resolve this error without needing Oracle Support – though their My Oracle Support note provides additional troubleshooting. Ora-27103 Internal Error Svr4 Error 11 Resource Temporarily
Reboot or re-login as oracle.