From a1e28d35051b492cfe84d6565e9be8494b61c6f3 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Mon, 27 Aug 2001 23:42:34 +0000 Subject: [PATCH] Fix some typos. --- doc/src/sgml/maintenance.sgml | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml index 7629c5bd54..ff7f09a7fd 100644 --- a/doc/src/sgml/maintenance.sgml +++ b/doc/src/sgml/maintenance.sgml @@ -1,5 +1,5 @@ @@ -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 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.) @@ -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: every table - in the database must be VACUUMed more often than once every billion - transactions. + restart. The price is this maintenance requirement: + every table in the database must be VACUUMed at least once every + billion transactions. @@ -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 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 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 frozen). This policy means - that the maximum safe interval between VACUUMs of any table + live and die without ever being frozen). With this policy, + the maximum safe interval between VACUUMs 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 VACUUM FREEZE is performed in an otherwise-idle database, it is guaranteed that 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 initdb to prepare the template0 database. It should also be used to prepare any -- 2.40.0