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 11.2.0.2 _serial_direct_read
parameter was a Boolean, and starting from 11.2.0.2 the
datatype was changed to VARCHAR2".
- In 11.2.0.1 the default value was
_serial_direct_read=false. Since the advent of
11.2.0.2 it changed to _serial_direct_read="auto".
- Release 11.2.0.1 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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