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Don Burleson Blog 







_serial_direct_read tips

Oracle Database Tips by Donald BurlesonJune 7, 2015


Question:  Can you shed some light on the _serial_direct_read parameter?  I understand that _serial_direct_read has something to do with full-table scans but the _serial_direct_read parameter is undocumented.


Answer:  The _serial_direct_read parameter related to the new 11g "smart scan" use with Exadata servers. Various web source have these important notes on _serial_direct_read:
  • Before release _serial_direct_read parameter was a Boolean, and starting from the datatype was changed to VARCHAR2".

  • In the default value was _serial_direct_read=false.  Since the advent of it changed to _serial_direct_read="auto".

  • Release adds a new feature "adaptive direct path reads".  The adaptive direct path reads" value is based on number of blocks in a table/index.  It is controlled by the hidden parameters: _adaptive_direct_read and _small_table_threshold.


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