Re: Physical Log size

Link, David A. <DALink@West.com> wrote in message news:7tjlri$ra$1@news.xmission.com... > > I have an OLTP database which I need to keep the checkpoints below 5 > seconds, however, my users need to load millions of records periodically. > The database needs to be available 7x24. I have LRUMIN=0 and LRUMAX=1. My > checkpoints still jump up during a load. My current physical log is 80 meg > in size. Are there any caveats to making this 500 meg, so I can avoid > reaching the 75% thresh hold? First of all, you must determine what causes your checkpoints - CKPTINTVL time or your phys. log becomes 75 % full. Respectively, increase your checkpoint interval or size of your physical log. With big phys. log you can perform checkpoint right after big load - when checkpoint duration not so critical. Of course, do not forget to perform checkpoint _BEFORE_ big load -this is critical for performance. > > Addition information is LRUS=24,CLEANERS=24. Depending on number of your CPUs and cleaners monitoring you can try to increase your CLEANERS value. Also, LRUS = 24 for what number of buffers ? Probably you must increase your LRUS. > > Is there anything else which I should try? > > My data is striped accross 8 drives and mirrored. When the dirty buffers are > flushed how is this handled? I have 1 dbspace and I am wondering if that is > making the flushing single threaded. No. During checkpoint Informix performs 'sorted' writes - dirty pages are sorted for every chunk and then written to disk in parallel. That's why you can try to set your CLEANERS equal to number of chunks in system if number of chunks is higher then 24 for your system. > > Is there anything else I should be looking at? Is your box NT or Unix ? Raw devices ? KAIO on or off ? > > iostat shows no hot disks. What about onstat -D, onstat -g iof, monitoring cleaners state during checkpoint ? ---------------------------------------------------- With best regards, Yuri Dovgart SAP R/3, Informix technical consultant, Senior System Consultant System Architecture and High Availability Systems, 'Telecominvest' company Email y_dovgart@tci.ukrtel.net ICQ 39284285