Re: 2 gig per raw space
In article <331F9977.613D@inconnect.com>, Thuc Nguyen <thucn@inconnect.com> writes >Hi everyone, > >I am with Online 5.03 on HP 9.02 > >My "Sr" DBA did not have full confidence in what I told him. > >I have seen the previous postings but did not save them. I need to prove >him that I am right by showing him your postings. > >Am I correct that there is limit of 2 gig per raw space? > Yes - Informix can only access the first 2 gigs of a chunk. Whatever the pathname of the chunk E.g. /tmp/chunk1 or /dev/fdsk/c0t1d0s0 Informix can only access the first 2 gigaytes. This means the combination of start offset of chunk + size of chunk must be exceed 2 gigabytes. >Am I correct that if we have 8 gigs of hard disk then we will have 4 two >gigs raw spaces? > Correct although you may need to partition the disk first. E.g. on suns use format/fdisk and create 2 gigabyte slices. i.e. partition 1 = 2 gigs = /dev/rdsk/c?t?d?s1 partition 4 = 2 gigs = /dev/rdsk/c?t?d?s4 partition 5 = 2 gigs = /dev/rdsk/c?t?d?s5 Otherwise you may need to use a Logical Volumn Manager (LVM) to split the disk into 2 giga parts. E.g. via SAM on HP-UX. >Example: > >/dev/ifmx/coris0 2 gigs >/dev/ifmx/coris1 2 gigs >/dev/ifmx/coris2 2 gigs >/dev/ifmx/coris3 2 gigs > >Am I correct that there is no limit of gigs each dbspace? > There is a limit on the maximum number of chunks in the instance this is because only one page is allocated to store chunk information. To work out the maximum number of chunks under Online 5 do size of info used to track the chunk = (length of chunk pathname + 29 bytes) rounded up to the nearest multiple of 4. Total size available to store chunk information = online page size - 28 bytes. Eg chunk pathnames are all 10 bytes long and 2K page size. size of info used to track the chunk = (10 + 29 bytes) rounded up to the nearest multiple of 4 = 40 bytes. Total size available to store chunk information = 2048 bytes - 28 bytes. = 2028 bytes. Maximum number of chunks = 2040/40 = 50 chunks!!. See Informix Online Adminstrators Guide Version 5.0 Page 2-86. >Am I correct that the fragment can work on Online 5.03? if so, how much >is limited per dbspace? > You cannot fragment under Online 5 only Online 7. >BTW, I saw the log file. It said, something like "time out..page >cleaner" What does it mean? Is it running out of page cleaner? There >was four page cleaners in the tbconfig file. > Ech page cleaner is allowed 120 seconds from when it starts page cleaning before online writes this message to the log file. It means a page cleaner started page cleaning and 120 seconds later was still page cleaning i.e. had not finished. This is a warning rather than an error i.e. nothing has "gone wrong" but it does mean you should look at how page cleaning is down (for performance reaons). Try adding more page cleaners or decreasing the LRU_MIN_DIRTY and LRY_MAX_DIRTY parmeters in Onlne. I would first add 2 page cleaners and see if that helps. >I understand the extent size method but how can I determine how much I >need to add to the next size? > Either a) Do alter index {indexname} to cluster for an index on the table or b) unload/reload the table. Then use tbcheck -pe | grep <tablename> to see the size of the table in pages. Do this 1 weeks apart and take 6 times the difference (i.e. 6 weeks, 3 months worth of growth). Repeat each month to monitor how fast each table grows. >Thanks in advance for your reply. > OK. >Thuc -- David Williams