Oracle Hidden Parameters


Oracle initialization or INIT.ORA parameters with an underscore in front are hidden or unsupported parameters. One can get a list of all hidden parameters by executing this query:

SELECT *
  FROM SYS.x$ksppi
 WHERE SUBSTR (ksppinm, 1, 1) = '_';

The following query displays parameter names with their current value:

SELECT   a.ksppinm "Parameter", b.ksppstvl "Session Value",
         c.ksppstvl "Instance Value"
    FROM x$ksppi a, x$ksppcv b, x$ksppsv c
   WHERE a.indx = b.indx AND a.indx = c.indx AND SUBSTR (ksppinm, 1, 1) = '_'
ORDER BY a.ksppinm;

Remember: Thou shall not play with undocumented parameters! Using undocumented parameters without the consent of Oracle Support will make your database “un-supported”. You will be on your own if the parameters you’ve set cause problems or data corruption.

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