suggestions on vacuum

If we are running critical applications that need to have all time
access(select,insert,delete,update,create,etc...) to a database, what
are my options on running a vacuum? Is this vacuum feature only in
Posgres database or is in all databases? I don't think there is
something like this in Oracle, and if we can't figure out a workaround
we might then need to use other database. Any suggestions? We expect it
to do a lot of transactions and _probably_ will need to run vacuum
daily.

Thanks

- John

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