DBCA fails with error message ORA-27104 on Linux
[ 2017-09-03 20:49:06.137 CEST ] Creating and starting Oracle instance
DBCA_PROGRESS : 1%
DBCA_PROGRESS : 2%
[ 2017-09-03 20:49:07.366 CEST ] ORA-27104: system-defined limits for shared memory was misconfigured
DBCA_PROGRESS : 3%
[ 2017-09-03 20:49:07.372 CEST ] ORA-01034: ORACLE not available
[ 2017-09-03 20:49:07.373 CEST ] ORA-01034: ORACLE not available
[ 2017-09-03 20:49:11.486 CEST ] DBCA_PROGRESS : DBCA Operation failed.
Kernel parameter shmall is set to 2097152 as documented in http://docs.oracle.com/cloud/latest/db112/LADBI/pre_install.htm#LADBI1187
Oracle Support Web mentions document Doc ID 1922934.1 with Bug 14202016 (LNX64-12.1-BC:DBCA FAILED TO CREATE POLICY DB DUE TO ORA-27104). A one-off patch can be demanded or as a workaround shmall can be increased to 9272480:
The following command sets the change immediately
sysctl -w kernel.shmall=9272480
Additionally, it is necessary to make the changes persistent in files like /etc/sysctl.conf (or better in a separate file that is also loaded during reboot) with an entry
kernel.shmall=9272480
