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The blocks written out are the least
recently used blocks. Writing blocks in this order minimizes the performance
impact of losing them from the buffer cache.
Instance Memory and Processes | 53
Log Writer (LGWR)
Writes the redo information from the log buffer in the SGA to all copies of the
current redo log file on disk. As transactions proceed, the associated redo information
is stored in the redo log buffer in the SGA. When a transaction is
committed, Oracle makes the redo information permanent by invoking the Log
Writer to write it to disk.
System Monitor (SMON)
Maintains overall health and safety for an Oracle instance. SMON performs
crash recovery when the instance is started after a failure and coordinates and
performs recovery for a failed instance when youhave more than one instance
accessing the same database, as with Real Application Clusters. SMON also
cleans up adjacent pieces of free space in the datafiles by merging them into one
piece and gets rid of space used for sorting rows when that space is no longer
needed.


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