REINDEXing user table in non stand-alone?

Hi,

I read the manual for the REINDEX command.
The REINDEX command is described as

    "Recover corrupted system indexes under
    stand-alone Postgres "

I am currently trying to reindex an user table.
Does one need to go into stand-alone mode to
reindex an user table?

I have actually REINDEXed an user table when
the database is not in stand-alone mode. It
seems fine but the test environment does not
have much users accessing it, the live site that
I eventually want to REINDEX does.

Is it safe to REINDEX an user table while in
non stand-alone mode when other users are
accessing it?

Thank you in advance.