ORA-27101: shared memory realm does not exist

ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist

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Cause: Unable to locate shared memory realm
Action: Verify that the realm is accessible

Explanation:

you could be receive ORA-27101 because you tried to modify the database parameters such as SGA_MAX_SIZE size. You can try to bring back the original parameters.

C:\Documents and Settings\Administrator>sqplus /nolog

– SQL> conn / as sysdba;

– SQL> shutdown immediate;

– SQL> startup pfile=’D:\oracle\product\10.2.0\admin\wiapps\pfile\init.ora.112320071736′;

– SQL> create spfile from pfile;

– SQL> shutdown immediate;

– SQL> startup;

This logic is startup with pfile and copy oracle parameter in pfile to spfile, then startup with new spfile.