SMON -> performs recovery, when instance fails and,
PMON -> performs recovery, when user process fails.
PMON
• Rolls back the user’s current transaction
• Releases all the locks that are held on tables or rows
• Frees other resources used by the users
• Restarts the dead dispatcher
SMON
• Rolling forward changes that are made in the online redo log files but
not in the data files. Since all the committed transactions are written
to the online redo log files, these are successfully recovered as
result of rolling forward changes from the online redo log files to the
data files.
• Opening the database. After the database is opened, users can log on
and access any data that is not locked by un-recovered transaction.
• Rolling back all the uncommitted transactions.