Re: Row Devices and Chunk offset
sujata_soman_at_omm-la2-infotech-001@internet.omm.com wrote: > > Hi all. > We are running Informix 7.22 on out IBM machines ( AIX ) and have > not specified any offset. I do not know why you are facing any > problems. There is no such requirement that I know of > Can you give me some more specifications ( since I deleted your > original message by mistake ) and then I may be able to help you. > > Sujata > > ______________________________ Reply Separator _________________________________ > Subject: Re: Row Devices and Chunk offset > Author: Jonathan Leffler <johnl@informix.com> at internet > Date: 10/15/97 8:54 AM > > 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> > > Well, I have seen AIX and Solaris installations (both 5 and 7) without offset that work fine. On the other hand, when you create a fresh logical volume on AIX and dump first several bytes, they do contain something (LV name etc). Curious. Dragi "Bonzi" Raos +--------------------------------------------------------+ | 4-MATE Information Engineering Inc. | +--------------------------+-----------------------------+ | 4-MATE | Tel: +385 (1) 242-116 | | Kosa bb | +385 (1) 242-126 | | 10000 Zagreb | Fax: +385 (1) 242-121 | | Hrvatska (Croatia) | e-mail: bonzi@4mate.hr | | | URL: http://www.4mate.hr | +--------------------------+-----------------------------+