Re: write to disk in cooked files

Also sprach Neil Truby <ntruby@netcomuk.co.uk> : :guest wrote: :> :> Hi , :> When we are using cooked files , when a write is issued by informix to the :> OS "UNIX" it returns a write successful . Now my question is where exactly is :> the write performed i.e to the buffer or to the disk ? : :Well, the point is, you don't know. And becuase you can't be certain :that the write HAS actually gone to disk, as Informix assumes it has, :you have potential data integrity problems. : :This is why, correctly in my opinion, Informix recommend that you use :raw disk for important (ie non-development) systems. An exception is, :arguably, temporary dbspaces. Well, yes and no. Indeed, what Niel writes is the conventional wisdom. However, for some number of years now, Informix has been opening chunks with the O_SYNC flag (I know - I peeked at the source), which, on a well-behaved Unix system, causes the write to be flushed to disk immediately, i.e. the data won't be hanging about in a Unix f/s buffer somewhere. What this in turn does to your i/o performance is another matter. But the data *should* be getting to disk. Dave Dave Kosenko (posting from home) Currently teaching folks everything I know about Informix at Summit Data Group (an Informix Authorized Education Center) For more info, see http://www.summitdata.com ********** "Everybody plays the fool, sometimes."