Re: Upgrade to 11.70 from 11.50 results in low Read Ahead Utilization

Hi Richard, 1) The first time the query encounters a page needing to be read from disk, read-ahead will be turned on. 2) May want to check out this blog: http://jfmiii.com/informix/?p=107 3) The new read-ahead algorithm replaces the old algorithm completely (changes include new readahead threads that take the burden of dealing with the read-ahead code off of the query threads). > > > From: Richard Kofler <richard.kofler@chello.at> > To: informix-list@iiug.org > Date: Sat, 30 Jul 2011 15:51:48 +0200 > Subject: Re: Upgrade to 11.70 from 11.50 results in low Read Ahead Utilization > Hi Hyun-Ju, > > Am 30.07.2011 05:28, schrieb Hyun-Ju Vega: >> >> Hi, >> >> In 11.70.xC3, the new AUTO_READAHEAD ONCONFIG parameter was introduced. >> >> This parameter reflects a new read-ahead algorithm in the database server. >> >> Basically, in mode 1 setting, auto read-ahead will turn off >> read-aheads for a scan if it detects that the pages are already cached >> in the buffer pool. If the database server detects that the query is >> encountering I/O, it will turn on read-aheads again for the >> > > how fast will this be detected? And how fast will RA start again? > > ... > > -- > Richard Kofler > SOLID STATE EDV > Dienstleistungen GmbH > Vienna/Austria/Europe > Hyun-Ju