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NAME="NON-DURABILITY"
>14.5. Non-Durable Settings</A
></H1
><P
> Durability is a database feature that guarantees the recording of
committed transactions even if the server crashes or loses
power. However, durability adds significant database overhead,
so if your site does not require such a guarantee,
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> can be configured to run
much faster. The following are configuration changes you can make
to improve performance in such cases. Except as noted below, durability
is still guaranteed in case of a crash of the database software;
only abrupt operating system stoppage creates a risk of data loss
or corruption when these settings are used.
<P
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></P><UL
><LI
><P
> Place the database cluster's data directory in a memory-backed
file system (i.e. <ACRONYM
CLASS="ACRONYM"
>RAM</ACRONYM
> disk). This eliminates all
database disk I/O, but limits data storage to the amount of
available memory (and perhaps swap).
</P
></LI
><LI
><P
> Turn off <A
HREF="runtime-config-wal.html#GUC-FSYNC"
>fsync</A
>; there is no need to flush
data to disk.
</P
></LI
><LI
><P
> Turn off <A
HREF="runtime-config-wal.html#GUC-FULL-PAGE-WRITES"
>full_page_writes</A
>; there is no need
to guard against partial page writes.
</P
></LI
><LI
><P
> Increase <A
HREF="runtime-config-wal.html#GUC-CHECKPOINT-SEGMENTS"
>checkpoint_segments</A
> and <A
HREF="runtime-config-wal.html#GUC-CHECKPOINT-TIMEOUT"
>checkpoint_timeout</A
>; this reduces the frequency
of checkpoints, but increases the storage requirements of
<TT
CLASS="FILENAME"
>/pg_xlog</TT
>.
</P
></LI
><LI
><P
> Turn off <A
HREF="runtime-config-wal.html#GUC-SYNCHRONOUS-COMMIT"
>synchronous_commit</A
>; there might be no
need to write the <ACRONYM
CLASS="ACRONYM"
>WAL</ACRONYM
> to disk on every
commit. This setting does risk transaction loss (though not data
corruption) in case of a crash of the <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>database</I
></SPAN
> alone.
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