Excerpts from Bruce Momjian's message of lun ago 23 14:55:55 -0400 2010: > OK, I have attached a proposed patch to improve this. I moved the > pg_clog mention to a new paragraph and linked it to the reason the > default is relatively low. > > Comments?
I think the new para doesn't make much sense, in context. Why does it say "freeze"? How can we expect users to understand how that is related to this parameter? > --- 4150,4165 ---- > <para> > Specifies the maximum age (in transactions) that a table's > <structname>pg_class</>.<structfield>relfrozenxid</> field can > ! attain before a <command>VACUUM</> freeze operation is forced > ! to prevent transaction ID wraparound within the table. > ! Note that the system will launch autovacuum processes to > ! prevent wraparound even when autovacuum is otherwise disabled. > ! </para> > ! > ! <para> > ! Vacuum freeze also allows removal of old files from the > ! <filename>pg_clog</> subdirectory, which is why the default > ! is a relatively low 200 million transactions. > This parameter can only be set at server start, but the setting > can be reduced for individual tables by > changing storage parameters. -- Álvaro Herrera <alvhe...@commandprompt.com> The PostgreSQL Company - Command Prompt, Inc. PostgreSQL Replication, Consulting, Custom Development, 24x7 support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers