Explanation:
PMON background process cleans up the failed connections. The process monitor performs process recovery when a user process fails. PMON is responsible for cleaning up the cache and freeing resources that the process was using. PMON also checks on dispatcher and server processes and restarts them if they have failed. Incorrect Answer:
1: The archive copies the online redo log files to archival storage after a log switch has occurred.
2: At specific times, all modified database buffers in the SGA are written to the data files by DBWn. This event is called a checkpoint. The checkpoint process is responsible for signaling DBWn at checkpoints and updating all the data files and control files of the database to indicate the most recent checkpoint.
3: The database writer writes modified blocks from the database buffer cache to the data files.
4: The log writer writes redo log entries to disk. Redo log entries are generated in the redo log buffer of the SGA, and LGWR writes the redo log entries sequentially into an online redo log. If the database has a multiplexed redo log, then LGWR writes the redo log entries to a group of online redo log files.
6: The system monitor performs recovery when a failed instance starts up again. With Real Application Clusters, the SMON process of one instance can perform instance recovery for other instances that have failed. SMON also cleans up temporary segments that are no longer in use and recovers terminated transactions skipped during recovery because of file-read or offline errors. These transactions are eventually recovered by SMON when the table space or file is brought back online. SMON also coalesces free extents in the dictionary managed table spaces to make free space contiguous and easier to allocate.
Reference:
OCP Oracle 9i Database: Fundamentals II Exam Guide, Rama Velpuri, p. 174-175
Chapter 7: Instance and Media Recovery Structures

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