Hidden Parameters

 

Hidden Parameters 

Parameters that begin with an underscore, such as 

_USE_VECTOR_POSTS, are hidden parameters. You will not find 

them in V$PARAMETER, or see them with the SHOW PARAMETERS 

command, because they are hidden. You certainly will not find them 

explained in the Oracle documentation, because they are 

undocumented. You can, however, get their descriptions with the APT 

script hidden_parameters.sql and check their values with the script 

all_parameters.sql . 

Some hidden parameters are operating system specific. Some are 

needed only in unusual recovery situations. Some are used to disable 

or enable new features. And many are related to obscure performance 

issues. As with all undocumented features, hidden parameters may 

disappear or change in a future release. You should therefore use them 

as a last resort, and only after checking with Oracle Support, and 

documenting the issues fully for your successor. 

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