单项选择题 You company has four DBAs. You need to know which DBA added a column to the JOB_HISTORY table. The database cannot be offline during work hours. Which LogMiner command can you use to find out which user made the table change？（）

单项选择题 You created a database by using the Database Configuration Assistant. What must you do to access a user account in the sample schemas？（）

多项选择题 The multithreaded agent architecture for heterogeneous services is similar to the Oracle multithreaded server architecture. The principal difference is that it used threads instead of processes.  What are thee kinds of threads that it uses？（）