New answers tagged parameter
2
You'd need to add IS_SPECIFIED (or ISSPECIFIED) to the where clause, as some hidden parameters may be set by... other things.
A parameter can be removed from an spfile by issuing:
ALTER SYSTEM RESET "_some_hidden_parameter" scope = spfile;
You will likely have to stop and start the instance(s) to have the changes take effect.
2
Create a pfile from the spfile:
CREATE PFILE FROM SPFILE;
Edit the generated pfile and remove the parameters, then recreate the spfile from the edited pfile. Bounce the database & all should be well.
The database might need to be down when you recreate the spfile from the pfile.
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