Oracle is the industry standard for databases, no one will argue here. After acquiring Sun Microsystems they have also become one of the leaders as telco-grade systems supplier (HW + OS + DB). Most admins know the basics about how Oracle works, how to start it up, shut it down, and with a bit of googling, how to restore and backup the db.
I had a similar problem today (our DBA is on holiday) and we needed to quickly restore the DB to proper operation.
For those of you looking for a quick cheat-sheet on how to do the basics with Oracle I have prepared a reference page.
Best book for beginner DBA: here.