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Fix some typos.

This commit is contained in:
Tom Lane 2001-08-27 23:42:34 +00:00
parent 7d66bf261c
commit a1e28d3505
1 changed files with 9 additions and 9 deletions
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18
doc/src/sgml/maintenance.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.1 2001/08/26 21:17:12 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.2 2001/08/27 23:42:34 tgl Exp $
-->
<chapter id="maintenance">
@ -226,7 +226,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.1 2001/08/26 21:17:12
than 4 billion transactions) will suffer <firstterm>transaction ID
wraparound</>: the XID counter wraps around to zero, and all of a sudden
transactions that were in the past appear to be in the future --- which
means their outputs become invisible. In short, catatrophic data loss.
means their outputs become invisible. In short, catastrophic data loss.
(Actually the data is still there, but that's cold comfort if you can't
get at it.)
</para>
@ -237,9 +237,9 @@ $Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.1 2001/08/26 21:17:12
transactions. This of course was not very satisfactory for high-traffic
sites, so a better solution has been devised. The new approach allows an
installation to remain up indefinitely, without initdb or any sort of
restart. The price is this maintenance requirement: <emphasis>every table
in the database must be VACUUMed more often than once every billion
transactions</emphasis>.
restart. The price is this maintenance requirement:
<emphasis>every table in the database must be VACUUMed at least once every
billion transactions</emphasis>.
</para>
<para>
@ -261,7 +261,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.1 2001/08/26 21:17:12
Therefore, once a tuple has been created with a particular normal XID, the
tuple will appear to be <quote>in the past</> for the next two billion
transactions, no matter which normal XID we are talking about. If the
tuple still exists after more than two billion transactions, it would
tuple still exists after more than two billion transactions, it will
suddenly appear to be in the future. To prevent data loss, old tuples
must be reassigned the XID <literal>FrozenXID</> sometime before they reach
the two-billion-transactions-old mark. Once they are assigned this
@ -276,8 +276,8 @@ $Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.1 2001/08/26 21:17:12
to any tuple with a normal XID more than one billion transactions in the
past. This policy preserves the original insertion XID until it is not
likely to be of interest anymore (in fact, most tuples will probably
live and die without ever being <quote>frozen</>). This policy means
that the maximum safe interval between <command>VACUUM</>s of any table
live and die without ever being <quote>frozen</>). With this policy,
the maximum safe interval between <command>VACUUM</>s of any table
is exactly one billion transactions: if you wait longer, it's possible
that a tuple that was not quite old enough to be reassigned last time
is now more than two billion transactions old and has wrapped around
@ -335,7 +335,7 @@ VACUUM
to be considered good by all open transactions. In particular, if
a <command>VACUUM FREEZE</> is performed in an otherwise-idle database,
it is guaranteed that <emphasis>all</> tuples in that database will be
frozen. Hence, as long the database is not modified in any way, it
frozen. Hence, as long as the database is not modified in any way, it
will not need subsequent vacuuming to avoid transaction ID wraparound
problems. This technique is used by <filename>initdb</> to prepare the
<filename>template0</> database. It should also be used to prepare any