Re: bufwaits and RA_PAGES

In article <380DAF04.D290D679@SPAMsiemens.at>, Wolf D. Pichler <wolf- dieter.pichlerBLOCK@SPAMsiemens.at> writes >Art, thanks for your reply > >> Your new RA parameters are IMMENSE, > >I agree with you, BUT take a look at my new onstat -p: > >INFORMIX-OnLine Version 7.23.UC3 -- On-Line -- Up 6 days 17:12:05 -- 266024 >Kbytes > >Profile >dskreads pagreads bufreads %cached dskwrits pagwrits bufwrits %cached >14853249 21452721 440733276 96.63 3003612 6038936 15158192 80.18 > >isamtot open start read write rewrite delete commit rollbk > >276228144 1307835 2550587 243151708 1978592 709893 2025501 760813 96 > >ovlock ovuserthread ovbuff usercpu syscpu numckpts flushes >300 0 0 122651.72 32464.29 1682 3848 > >bufwaits lokwaits lockreqs deadlks dltouts ckpwaits compress seqscans >595469 361 504643120 0 0 797 324649 2319 > >ixda-RA idx-RA da-RA RA-pgsused lchwaits >5358224 975963 5029247 11357347 93803 > > RA-pgused -------------------- ixda-RA+idx-RA+da-RA looks close to 100% so it looks like you are using all the pages you are reading.. >> For the onstat -p you posted the formula >> gives: >> >> BR = (3187033 / (40054626 + 29804841)) * 100.00 = 4.56% >> >> Which is excellent! No worries mate. At least not on this one. >> > >My new BR=1.63% .... the bufwaits decreased significantly ... what is your >comment? > >All onstat -p parameters still seem to be ok to me, just the lchwaits seem to >have increased. >Possibly the BR improved although the immense values of the RA-parameters, >because our indices also are immense and scanned quite often. On this machine >we have a 2GB table with a 250MB index. So i assumed, that a 4MB read ahead is >nothing compared to the index size .... this is why i chose those immense >values. Can you add BUFFERS to imporve caching. Less disk I/O required reduces the effect of RA parameters and makes things faster. Caching from memort is better than read ahead,, >And this is just a small test configuration, the biggest index at one customer >is 1.2GB. Unfortunately i have no access to those machines now - so i cannot >check the situation there. >(BTW: we dont have real problems with the DB performance because the >application which uses the DB is so slow, that you dont notice even disastrous >misconfigurations. For example i saw a BR=11% yesterday ...but the customer >never protested ... ) > >> BTW I STRONGLY recommend AGAINST using >> RAID5 for Informix database disks > >I know, i know ... but i have no influence on that. Neither on hardware nor >on the database structure. > >But i changed the RA-parameters on a machine with RAID5 also .. the result was >the same .. new BR~=2% . > >Wolf D. Pichler > >Remove the uppercase words from my e-mail address to reply. > > -- David Williams