Re: Extents Overlap

At 03:12 PM 7/16/96 -0500, MSgt Doug White wrote: >We ran the TBCheck -ce and got the error message: > >ERROR extents overlap. > >TBCheck -pe helped us identify the Chunk and therefore the DBSpace > (thanks to Joe Lumbley and his fine survival guide. > >Perhaps in panic mode we overlooked it in our administrators guide, >but we could not find anything in our fine manual. Anyone know just >how bad this is, and is the fix to unload, drop, recreate and reload >the tables in that chunk? Let's start with TFM. I looked in the (you guessed it!) "Informix- OnLine Dynamic Server Administrator's Guide, Version 7.2, volume 1", where the index entry for extents includes a listing for "validating consistency", which then says "...Extents must not overlap. If this command detects errors, perform a data restore from dbspace backup." Perhaps we don't need to do this right away, though... You can check the physical structure of the pages with tbcheck -pP, and verify for yourself the exact nature of the error (if any.) This is covered in pretty thorough detail in the manual "Informix-OnLine 5.0 Internal Architecture and Advanced Administration Training Manual", available only by taking the course with a similar name. I *highly* recommend this course, BTW. When you reach the point where you are interested in the physical structure of data on disk and in memory this is one of the few places to find Informix training at that level. Still, in order to find out what this error means to you, there is more research to be done. First, if your extents really do overlap then you have terrible data corruption problems. The engine will be giving errors like crazy, puking all over your screen, and (depending on which extents are corrupted) might not even come online. There are situations where this error was erroneously generated. You can find them by checking (not TFM, but another information resource) your INFORMIXLINK web pages. (As far as I can tell you can find this with I-Link. From "the inside" I have a hard time determining what a paying customer can see. Please let me know if you can't see this information under "tech info".) One such error was caused by an improper sort on the extent addresses, causing the extents to seem to be overlapped, when they really weren't. Another had to do with the 4K page on IBM RS6000's not being properly handled. Lastly, a call to your friendly tech support representative would clear it up for sure. At last, someone has caused me to post, not RTFM, but "call TS". I hope your problem is simply an erroneous message. Clem ______________________________________________________ Clem Akins (aka clema@informix.com) Informix Software, Inc (Standard disclaimers apply) International Technical Support Last seen: in sunny Menlo Park, California