Determining if an Oracle Home is Read-Only
By default, an Oracle Database installation configures all Oracle Database homes in a read-only mode. You can use the Registry Editor to determine if your Oracle home is a read-only Oracle home.
Start Registry Editor and navigate to the ORACLE_HOME_READONLY entry in the HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\KEY_OracleHomeName Windows Registry key.
                  
The default value for the 
            ORACLE_HOME_READONLY parameter appears as Y in a read-only mode. Do not modify this value.
               Parent topic: Configuring Oracle Homes