Re: Read-ahead parameters

Doug McAllister wrote: > > I have read somewhere that the max value for read ahead is 32. I do not > remember where and I cannot find a reference to a max value in any doc. > Any references? I think this is based on our big buffer size of 32 pages which can be written in a single IO. I guess the recommendation for OLTP is to generate no more than a single IO for read ahead. But NOT if you are using light scans, because the RA parameters also define the number and size of the light scan buffers. But, as ever, I could be totally wrong. Where's Chris? By the way, this is all covered in the excellent course; "Informix Dynamic Server Performance Tuning". Cheers, -- Mark. +----------------------------------------------------------+-----------+ |Mark D. Stock - Informix SA http://www.informix.com |//////// /| |mailto:mdstock@informix.com http://www.informix.com/idn |///// / //| |http://www.iiug.org +-----------------------------------+//// / ///| | Tel: +27 11 807 0313 |What year 2000 bug? year 2000 bug? |/// / ////| | Fax: +27 838250 2325 |year 2000 bug? year 2000 bug? year |// / /////| |Cell: +27 83 250 2325 |2000 bug? year 2000 bug? year 2000 |/ ////////| +----------------------+-----------------------------------+-----------+