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1 | | -<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.307 2010/08/23 02:43:25tgl Exp $ --> |
| 1 | +<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.308 2010/08/24 13:32:25momjian Exp $ --> |
2 | 2 |
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3 | 3 | <chapter Id="runtime-config"> |
4 | 4 | <title>Server Configuration</title> |
@@ -4150,12 +4150,16 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv; |
4150 | 4150 | <para> |
4151 | 4151 | Specifies the maximum age (in transactions) that a table's |
4152 | 4152 | <structname>pg_class</>.<structfield>relfrozenxid</> field can |
4153 | | - attain before a <command>VACUUM</> operation is forced to allow removal |
4154 | | - of old files from the <filename>pg_clog</> subdirectory and prevent |
4155 | | - transaction ID wraparound within the table. Note that the system |
4156 | | - will launch autovacuum processes to prevent wraparound even when |
4157 | | - autovacuum is otherwise disabled. |
4158 | | - The default is 200 million transactions. |
| 4153 | + attain before a <command>VACUUM</> operation is forced |
| 4154 | + to prevent transaction ID wraparound within the table. |
| 4155 | + Note that the system will launch autovacuum processes to |
| 4156 | + prevent wraparound even when autovacuum is otherwise disabled. |
| 4157 | + </para> |
| 4158 | + |
| 4159 | + <para> |
| 4160 | + Vacuum also allows removal of old files from the |
| 4161 | + <filename>pg_clog</> subdirectory, which is why the default |
| 4162 | + is a relatively low 200 million transactions. |
4159 | 4163 | This parameter can only be set at server start, but the setting |
4160 | 4164 | can be reduced for individual tables by |
4161 | 4165 | changing storage parameters. |
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