Not just Oakland. The majority of the Bay Area exists to support commuting to San Francisco. The peninsula tech companies are actually a newer phenomenon.
Oakland exists as an industrial hub. Emeryville, on the other hand, exists as a suburb of San Francisco (though I think that with recent business expansion, it's becoming its own city). As far as I know, this is still the case, and more people live and work in Oakland than live in Oakland and commute into SF.
Employment/residence ratios
Emeryville 4.36 San Francisco 1.40 Oakland 1.06
and a few others FWIW
Berkeley 1.30 Dublin 1.05 Mountain View 1.47 Palo Alto 2.54 San Jose 0.88 (qualifying it as largest suburb in the US, IMO)