doc: Improve description of data checksums
This partially reverts that got incorrectly merged, and this
improves the wording of the documentation that existed before that.
Per discussion with Justin Pryzby.
Discussion:
</indexterm>
<para>
- By default, data pages are not protected by checksums, but this can optionally be
- enabled for a cluster. When enabled, each data page will be ASSIGNED a
- checksum that is updated when the page is written and verified each time
+ By default, data pages are not protected by checksums, but this can
+ optionally be enabled for a cluster. When enabled, each data page includes
+ a checksum that is updated when the page is written and verified each time
the page is read. Only data pages are protected by checksums; internal data
structures and temporary files are not.
</para>
<para>
- Checksums verification is normally ENABLED when the cluster is initialized using <link
+ Checksums are normally enabled when the cluster is initialized using <link
linkend="app-initdb-data-checksums"><application>initdb</application></link>.
They can also be enabled or disabled at a later time as an offline
operation. Data checksums are enabled or disabled at the full cluster
- level, and cannot be specified for individual databases or tables.
+ level, and cannot be specified individually for databases or tables.
</para>
<para>
</para>
<para>
- When attempting to recover from corrupt data, it may be necessary to bypass
- the checksum protection. To do this, temporarily set the configuration
- parameter <xref linkend="guc-ignore-checksum-failure" />.
+ When attempting to recover from page corruptions, it may be necessary to
+ bypass the checksum protection. To do this, temporarily set the
+ configuration parameter <xref linkend="guc-ignore-checksum-failure" />.
</para>
<sect2 id="checksums-offline-enable-disable">
