audit_trail question 9.2/10.2

If using a pfile, what goes in sys.aud$ when audit_trail is set to DB? We ran into a scenario where we want to change auditing on a DB, but the pfile has audit_trail=NONE, hence we have to bounce. I think if we set it to DB across the enterprise, we can turn auditing on and off at will via the 'AUDIT XXX' command. Does setting this parm to DB have any effect other than allowing you to turn auditing on and off, and directing the audited information to sys.aud$? Does simply setting it to 'DB' cause info to go in the sys.aud$, even if you haven't enabled auditing?

Thanks- Chris

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