[systemd-devel] systemd (user) and (sd-pam) (user) processes in login shell

[Niksa Jurinovic]

Hello,

I am new to systemd init system as well as to fresh installed Fedora 23
Server, and I would like to put a question related to 'systemd (user)'
and '(sd-pam) (user)' processes invoked under each and every one user's
login shell. The first process is '/usr/lib/systemd/systemd --user' with
PPID=1 and the second is its child process '(sd-pam)'.  

What do these processes exactly do and why does my Oracle 12c
database instance (started by 'oracle' user) always crash (silently
shutdown by itself) WITHOUT these processes (or if they are killed)?
When it happens, the database instance is down, and the oracle alert.log
shows semaphore memory corruption:

ORA-27300: OS system dependent operation:semctl failed with status: 22
ORA-27301: OS failure message: Invalid argument
ORA-27302: failure occurred at: sskgpwrm1
ORA-27157: OS post/wait facility removed
ORA-27300: OS system dependent operation:semop failed with status: 43
ORA-27301: OS failure message: Identifier removed
ORA-27302: failure occurred at: sskgpwwait1
ksmsdes: Error destroying SGA
Instance termination got error 27120 from SGA destruction.

If these processes are active for 'oracle' user, Oracle instance never
crashes.

Thank you very much.