diff options
Diffstat (limited to 'doc/src/sgml/maintenance.sgml')
| -rw-r--r-- | doc/src/sgml/maintenance.sgml | 19 |
1 files changed, 9 insertions, 10 deletions
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml index f762c6ad44f..daee3b11891 100644 --- a/doc/src/sgml/maintenance.sgml +++ b/doc/src/sgml/maintenance.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.19 2002/09/21 18:32:53 petere Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.20 2002/11/11 20:14:03 petere Exp $ --> <chapter id="maintenance"> @@ -13,7 +13,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.19 2002/09/21 18:32:53 a regular basis to keep a <productname>PostgreSQL</productname> installation running smoothly. The tasks discussed here are repetitive in nature and can easily be automated using standard Unix tools such - as <filename>cron</filename> scripts. But it is the database + as <application>cron</application> scripts. But it is the database administrator's responsibility to set up appropriate scripts, and to check that they execute successfully. </para> @@ -104,7 +104,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.19 2002/09/21 18:32:53 <command>UPDATE</> or <command>DELETE</> of a row does not immediately remove the old <firstterm>tuple</> (version of the row). This approach is necessary to gain the benefits of multiversion - concurrency control (see the <citetitle>User's Guide</>): the tuple + concurrency control (see the &cite-user;): the tuple must not be deleted while it is still potentially visible to other transactions. But eventually, an outdated or deleted tuple is no longer of interest to any transaction. The space it occupies must be @@ -206,7 +206,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.19 2002/09/21 18:32:53 Although per-column tweaking of <command>ANALYZE</> frequency may not be very productive, you may well find it worthwhile to do per-column adjustment of the level of detail of the statistics collected by - <command>ANALYZE</>. Columns that are heavily used in WHERE clauses + <command>ANALYZE</>. Columns that are heavily used in <literal>WHERE</> clauses and have highly irregular data distributions may require a finer-grain data histogram than other columns. See <command>ALTER TABLE SET STATISTICS</>. @@ -299,7 +299,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.19 2002/09/21 18:32:53 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 - into the future --- ie, is lost to you. (Of course, it'll reappear + into the future --- i.e., is lost to you. (Of course, it'll reappear after another two billion transactions, but that's no help.) </para> @@ -311,17 +311,17 @@ $Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.19 2002/09/21 18:32:53 statistics in the system table <filename>pg_database</>. In particular, the <filename>datfrozenxid</> field of a database's <filename>pg_database</> row is updated at the completion of any - database-wide vacuum operation (ie, <command>VACUUM</> that does not + database-wide vacuum operation (i.e., <command>VACUUM</> that does not name a specific table). The value stored in this field is the freeze cutoff XID that was used by that <command>VACUUM</> command. All normal XIDs older than this cutoff XID are guaranteed to have been replaced by <literal>FrozenXID</> within that database. A convenient way to examine this information is to execute the query - <informalexample> + <programlisting> SELECT datname, age(datfrozenxid) FROM pg_database; </programlisting> - </informalexample> + The <literal>age</> column measures the number of transactions from the cutoff XID to the current transaction's XID. </para> @@ -336,7 +336,7 @@ SELECT datname, age(datfrozenxid) FROM pg_database; each database-wide <command>VACUUM</> automatically delivers a warning if there are any <filename>pg_database</> entries showing an <literal>age</> of more than 1.5 billion transactions, for example: - <informalexample> + <programlisting> play=# vacuum; WARNING: Some databases have not been vacuumed in 1613770184 transactions. @@ -344,7 +344,6 @@ WARNING: Some databases have not been vacuumed in 1613770184 transactions. or you may have a wraparound failure. VACUUM </programlisting> - </informalexample> </para> <para> |