The total available shared memory (stringMB) on the system was less than the chosen target database memory (stringMB).
Enter a value for target database memory that is less than stringMB.
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Try the following links for this error:
http://docs.oracle.com/cd/E16655_01/server.121/e26079/dbinstaller_errormessages.htm
https://community.oracle.com/message/4361316