RE: reasonable checkpoint interval
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}I disagree with the idea of increasing LRU writes and decreasing Chunk
}writes.
}The porblem with this is that Chunk writes are much faster then LRU writes.
} Chunk
}writes will be much faster since they will not be competing with other
}threads to do their work. Also Chuck writes work in sequence with the disk
}to shorten the amount of head movement while performing these writes.
}
}
}I think you need to balance LRU writes to allow the most amount of Chunk
}writes while not increasing forground writes and not increasing Check point
}time to an unexceptable time.
}
}Russ...
} __________________________________________
}
} Russell P. Kahler russell@oncontact.com
} (414)375-6540
} W67 N250A Evergreen Blvd.
} Cedarburg, Wi 53012
} ___________________________________________
}
}----------
}From: Chao Y. Din[SMTP:cdin@csc.com]
}Sent: Tuesday, July 02, 1996 9:23 AM
}To: informix-list@rmy.emory.edu
}Subject: Re: reasonable checkpoint interval
}
}Stuart Cracraft wrote:
}>
}> What is considered a reasonable informix checkpoint interval?
}>
}> I'm currently investigating a problem on a system with the checkpoint,
}> as shown in /usr/informix/online.log, occuring every 6 minutes or so.
}> This is on a Unix box with Informix 7.12.UC1.
}>
}> Users on PC's have a GUI application to do queries into this Informix
}> Online SQL engine. Every few minutes, their PC's freezeup (all
}> simultaneously) for up to 5 minutes reducing their productivity by
}> orders of magnitude.
}>
}> What checkpoint intervals are considered reasonable? Is there
}> such a thing as having checkpoint intervals too close together?
}> What are the Informix defaults?
}>
}> Users of this system are doing a moderate number of queries typically
}> against extremely large tables all indexed and multiply so. Meanwhile
}> a large number of system batch jobs are running doing lots of table
}> queries.
}>
}> Thanks ahead.
}>
}> --Stuart
}
}There is no short answer on this. The rule of thumb is to increase LRU
}Writes and Decrease Chunk Writes (check out "onstat -F"). A good
}reference, besides the admin guide, is "Informix - OnLine Performance
}Tuning" by Elizabeth Suto, published by Prentice Hall PTR.
}
}
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