Re: Row Devices and Chunk offset

On Wed, 15 Oct 1997, Philippe Meylan wrote: > We are using INFORMIX 7.1x and our chunks are located on row devices. IBM > inform us that an offset of 512 bytes is required between the base of the > row device and the beginning of the chunk. This area should be used by AIX > for system management. Not an unusual requirement, but a confounded nuisance. Many o/s make that sort of requirement, but often for more than 512 bytes. > My question : > > This requirement is undocumented By IBM? You seem to have found out about it... By Informix? It varies from platform to platform -- many machines don't need it; some do. On some machines, it depends on which raw device you are using. And, in any case, p15-6 of the version 7.2 OnLine DSA Server Admin's Guide discusses 'do you need to specify an offset?'. > and the ONINIT tools doesn't reserve any offset when creating a new > chunk. Unless you tell it to. One of the main purposes of the optional offset parameter is to avoid treading on the information required by the system. (The other purpose of the offset is to allow multiple chunks to share a single raw disk partition.) > It's this requirement justified This requirement is justified on machines where it is required, and not on machines where it isn't. > and can be applied on any platform? It can be used on any platform, but will waste space on platforms where it isn't needed. > Has Informix a document explaining that ? See the OnLine Admins Guide. Yours, Jonathan Leffler (johnl@informix.com) #include <witticism.h>