Re: The 2GB chunk size limit and Sparc storage arrays

The main reason for the 2 GB chunk size limit is that the lseek() system call takes a signed value for the offset type, and on a 32-bit machine, that means that the offsets which you can specify are limited to +/- 2GB. The code is designed to find a page within a dbspace in a single lseek() call. Removing this limitation would require one of several different possible fixes, and would depend on the hardware in use. You could arrange to call code that handles 64-bit offsets -- presumably a different system call. But this would require the code to create the correct offset, and so on. Or you could arrange to do multiple lseek() calls, doing a SEEK_SET to start, followed by a number of SEEK_CUR calls; this gets expensive. And so on. I do not know whether this limitation is to be removed in a forth-coming release. It is a common enough question, and while it is not too bad for a 20 GB database, if you start playing with TB (terabytes, or thousands of GB) then it rapidly becomes unusable. There are sound reasons (fragmented tables, partial restores) for having multiple dbspaces -- unless your database is headed for the TB range, I think you will be well advised to use multiple 2GB dbspaces anyway. You don't say which version of OnLine you are using, but unless you are using the leading edge products (7.1x), you are most unlikely to see this limitation removed -- if you are using 5.0x, forget it now. Yours, Jonathan Leffler (johnl@informix.com) #include <disclaimer.h> }From: Kevin McHugh <mkmchu@rmy.emory.edu> }Date: 18 Jan 1996 17:02:25 GMT }X-Informix-List-Id: <news.20385> } }Could the Informix monitors possibly reply to this question either }as a post or as a direct email? I am working at MCI on what is going }to be a rather large database. Although the 2G limit means more db- }spaces instead of a real wall on my storage capacity, I would prefer }to let Informix manage a 4G or 16G dbspace instead of managing a bunch }of 2G spaces. I anticipate being through the 2G barrier in about 6 }months. This may be a limit impossed by addressable space on a n-bit }machine. If this is so, then this limit should be made variable to }adjust to the machine the software is on. } } Finally, I would like to know who to contact for feature requests. }I would perfer email to calling the 800 number. } }Kevin McHugh }-- }mkmchu }+------------------------------+-------------------------+----------------+ }| Kevin McHugh - SW Engineer | mkmchu@fax.cs.mci.com | }| MCI Telecommunications Corp. | (719) 535-5278 | }+------------------------------+-------------------------+----------------+ }| ALL RIGHTS RESERVED. | }| This posting is copyright and may be used only for the purposes | }| of professional study. Use of this posting in any commercial | }| environment is explicity prohibited. This posting may only be | }| reproduced for personal archival purposes. | }+-------------------------------------------------------------------------+ }