Here's the book you need to prepare for Exam 1Z1-031: OCA/OCP: Oracle9i DBA Fundamentals I Study Guide

In-depth coverage of official exam objectives
Practical information on implementing and managing Oracle9i databases
Hundreds of challenging review questions, in the book and on the CD

Authoritative coverage of all exam objectives, including:
Understanding Oracle architecture and its main components
Identifying DBA administrative tools
Setting up password file authentications
Creating and managing Initialization Parameter Files
Configuring OMF
Create a database using Oracle Database Configuration Assistant
Creating a database manually