Re: Row Devices and Chunk offset

Dragi Raos <bonzi@4mate.hr> wrote: >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 Are you using a logical volume manager on these systems. I have a Solaris intallation where we are directly using the disk devices and we need to use an offset. On a another, larger Solaris system, we use Veritas for volume management. In this case, we don't use offsets. Barry Leb National Linen Service 1420 Peachtree Street MS #314 Atlanta, GA 30309 (404) 853-6119 (404) 853-6485 fax e-mail: barryleb@mindspring.com