cannot load such file -- dbi (LoadError)

[Fábio Weber]

I am a graduate student at the Federal University of Santa Maria,
Brazil and I need help with installing the DBI. I'm trying to run a
script, but this generates the following error:

/usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot
load such file -- dbi (LoadError)
       from /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in
`require'
       from /usr/local/oar/oaradmin.rb:16:in `<main>'

What am I doing wrong?

Att. Fábio Weber Albiero