umm it looks like about memory could you do a "top" command and check your memory resource.... but need more information.. which version obiee 18.104.22.168.0 , 22.214.171.124.0? which OS version?, could you post also the AdminServer.log & bi_server1.log..could you start the obiee 12c instance and after a time the bi server process crash?
Did you just update your repository? If yes, I'll suggest you look through this MOSC DOC with solution:
OBIEE 12c: OBI Server (obis1, nqsserver) Crashes On Start After Online Repository (RPD) Updates (Doc ID 2124489.1)
Obiee Version is: 126.96.36.199.0 (Build BIPS-20151008013645 64-bit)
OS is: Linux 3.8.13-118.4.2.el7uek.x86_64 #2 SMP Tue Mar 22 20:46:48 PDT 2016 x86_64 x86_64 x86_64 GNU/Linux
We tried to restart crasher server, but unable to restart. Yesterday, we upload repository using data-model-cmd.sh uploadrpd command since 'Copy Repository' bug issue.
After that, there were no problem. We worked on repository and analytics side until today.