NonStop SQL/MP Reference Manual

NonStop SQL/MP Reference Manual—142115
B-13
Considerations—BUFFERED
Buffering can improve transaction times by reducing the number of writes required
and by deferring writes so that the disk process can write a string of blocks in a
single I/O operation. However, buffering can cause loss of data on nonaudited files
if a failure occurs while updated rows are stored in cache memory but not yet
written to disk.
Audited files should always be buffered, because auditing itself protects against loss
of data. (Specifying NO BUFFERED for an audited file would unnecessarily reduce
performance.)
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AUDIT/BUFFERED relationship for tables
If you alter the AUDIT file attribute for a table, SQL automatically sets the
BUFFERED file attribute for that table (but not for its dependent indexes) as
follows:
°
If you specify AUDIT, SQL also sets BUFFERED.
°
If you specify NO AUDIT, SQL also sets NO BUFFERED.
To override the automatic setting, explicitly specify the BUFFERED file attribute in
the ALTER TABLE statement that changes the AUDIT attribute.
Altering the BUFFERED attribute does not affect the AUDIT attribute.