New answers tagged parameter
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.
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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