Re: How to size the logical log ?

In article <6gdono$8f1$1@news.xmission.com>, Timothy_Lam@crow.bmc.com wrote: > > > Hello Guys, > > Does anybody know how to calculate the size of the logical logs ? > > What does the logical log size based upon ? What are the factors ? > > I want to backup the logical logs very often to avoid disaster. > > How does informix backup logical logs ? > > Rdgs > Timothy > > I've read somewhere a rule of thumb - either in E. Suto's Informix Performance Tuning or R.D.Schneider's Optimizing Informix Apps, but not shure: Spend 10% of what your database will be in size for the sum of Logical and Physical Log: 7.5% for the Logical Log, and 2.5% for Physical Log. BUT: If you expect heavy insert/update/delete my experience is that 15% (1:3 Phys:Log-Log) is better Basically, if I am remember well, you have to look at the fact, that a transaction is counted as a long transaction (and therefore rolled back by the INFORMIX server), if all the other tranactions running fill the Logical Log up to the lower of the 2 LTX High Water Marks (LTHHWM - my default is 50, my actual value chosen is 60). I.e. you will have to look at that & you must avoid situations, where the Logical Logs fill up quickly while a transaction is waiting for commit or rollback. We have a lot of such transactions (XA) I control this by comparing onstat -l (U---C* in the flags is the UniqueID of the current log) with onstat -x showing UniqueIDs of used LogicalLog parts in the column with the header 'log', if >0 there. The idea here is that you will learn from this outputs, how 'far away' the mimimum UniqueID from onstat -x is from the current UniqueID. If you have 20 LL parts and this span is >10 the respective transaction is counted as a LongTransaction, if LTXHWM is set to 50%. With my setup this will only happen if the span is >12, as my LTXHWM is 60. I had to spend more space for the LogicalLog AND to increase LTXHWM & LTXEHWM to 60/70 to avoid too many transaction aborts If you run into that LongTransaction problem you will be hinted by the header of any onstat output [even 'onstat -', very short :-)] by the text (LONGTX) or Blocked by LTX (spelling may be incorrect), depending if you are over LTXHWM or over LTXEHWM percentage. Remember: LTXEHWM must be > LTXHWM and <= 100 I am on SNI SINIX 5.43 & INFORMIX V7.12 UC1 After all: Sorry for the my poor english, maybe a native speaker can get the idea and formulate this way better than me. Hope it helps. Regards Dick Richard Kofler EDVg-debis Systemhaus Vienna, Austria e-mail: richard_kofler@edvg.co.at -----== Posted via Deja News, The Leader in Internet Discussion ==----- http://www.dejanews.com/ Now offering spam-free web-based newsreading