ORA-27102: out of memory
I'm presuming you don't have metalink as this was the first hit:

SYMPTOMS

Instance not reachable and process dying. 

Background processes are dying and oracle is unable to spawn new processes. Clients cannot connect and they receive error:

java.sql.SQLRecoverableException: ORA-01034: ORACLE not available
ORA-27102: out of memory
Linux-x86_64 Error: 12: Cannot allocate memory
Additional information: 2673
Additional information: 488341508
Additional information: 1744830464


When this happens local connections are not possible, but already existing connections continue to work. The problem appears when running backups or complex queries then it disappears.

No specific memory related error is reported on the server log just logs like this one:

Errors in file /u01/app/oracle/diag/rdbms/alma/ALMA2/trace/ALMA2_cjq0_6234.trc:
Process J000 died, see its trace file
Thu Apr 06 14:25:40 2017
kkjcre1p: unable to spawn jobq slave process   &lt;=============  important symptom
Thu Apr 06 14:25:40 2017
Errors in file /u01/app/oracle/diag/rdbms/alma/ALMA2/trace/ALMA2_cjq0_6234.trc:
Process PPA2 died, see its trace file
Process J000 died, see its trace file
Thu Apr 06 14:25:42 2017
kkjcre1p: unable to spawn jobq slave process


CAUSE

This is was investigated in 


  Bug 24921392 CJQ FAILED TO SPAWN SLAVE PROCESS KKJCRE1P: UNABLE TO
  SPAWN JOBQ SLAVE PROCESS


The problem may be seen if MEMORY_TARGET is used and memory or swap space is under pressure.

SOLUTION

Apply patch 24921392 if available

OR 

As a workaround, increase memory and/or swap on the affected system to avoid the issue.