Tragedy affects people in different ways. For Barbara Gordon, it changed her entirely. After being Batgirl for a long time, the Joker came in and ruined her career by shooting her in the stomach, injuring her spine, and making her paralyzed. Batgirl was done.
But she didn't stay down long. Knowing she couldn't let Joker be the end note, she took to her remarkable computer skillset and became Oracle. As Oracle, Barbara became just as invaluable. She would help Batman and the others through virtually any situation she was called upon to help with. Whether it was getting intel, recon via security cameras, or using her hacking to break into anything electronic.
Even though Barbara isn't Oracle right now, she still has the skills, and her time as Oracle has been shown in various medium throughout the years.