Re: informix vs oracle

mail@markscranton.com wrote: > To all - > > I just returned from Mexico and Tokyo, and have some good news for the > Informix faithful...In Mexico, Informix is still leading Oracle in > market share. No - I don't know the percentages. We will continue to > visit Mexico clients to support these accounts, and grow new business. > > In Brazil, a very large Informix customer is starting a migration to > Informix from Oracle. This is very good news. > > Also, in Tokyo, we are securing consulting resources to help one of > Japan's largest Informix customers migrate some of their systems from > Oracle to Infomix as well. > > By the way, I'm not looking to compare "how many have migrated from > Informix to Oracle" over the last couple of years versus the inverse. > We are very aware of those situations. I just felt this was info the > Informix community should be aware of to help further the cause. > > Thanks, > Mark Scranton > > utkanbir wrote: > >>Hi Gurus , >> >>After 7 years with informix and 2 years with oracle , these are my > > own > >>comments about them. All the comments / corrections are wellcomed: >> >>1. backup / restore >> >>informix : the backup set is a complete object . It does not depend >>anything .It can be used as the only object in order to do restore. >> >>oracle : lots of things must be considered. You must know what you >>do. 'I just want to backup and restore my db ' is not enough. To do > > a > >>complete restore of the db , first it is necessary to copy all the >>files to a backup location (including datafiles,control files, undo >>and redo log?no be careful if you want to recover the db after > > copying > >>files back , you need current logs so backing up redo logs are not >>necessary . On the other hand copying entire datafiles before any > > type > >>of incomplete recovery is very important . (in order to restore a db > > , > >>copying the files once again huh...) And dont expect the ontape -r >>command's lovely message: do you want to backup the current logs? No >>such a thing exist....) >> >>If someone who only knows oracle ,doesnt know aynthing about the > > other > >>databases , this backup method can be the best one. But if you know >>the other databases restore backup methods, oracle method is much > > more > >>difficult and complex. >> >> >>2. Parallel query >> >>oracle : parallel query bypasses the buffer cache. it directly reads >>data from the disk into the user process's pga memory . It also does >>not check whether a block is cached in memory or not , it reads the >>disk every time. So same parallel query executed several times makes >>the same amount of disk io . >> >> >>On the other hand , parallel query architecture is more flexible than >>informix. It does not depend on tablespace number / partition . And >>parallel dml , parallel optimizer hints are very rich. (last veison > > of > >>informix i used is 9.2 so may be informix have some improvments which >>i dont know) >> >> >> >>3. Nologging operations: >> >> >>In oracle , it is possible to do certain operations without > > generating > >>redo log . These are called unrevorable operations : >> >>create table test nologging as (select * from dual)>> >>insert /*+append */ into a select * from dual >> >>these operations is not logged in redo logs so cant be reovered. >> >>But the drawback of such an operation is , if you have to recover the >>db server or datafile by using redo logs , the entire table becomes >>useless. Not >>only these insert statements are invalid but also the whole table. >> >>4. multi-versioning >> >>oracle has no dirty read concept but instead multi-versioning . So if >>session a updates data , session b see the previous version of the >>recods .But this can also happen for a long running queries!Although >>no updates take place , lots of different versions can be put in >>memory especially if your db is a datawarehouse type. >> >> >>Kind Regards, >>hope Is there a source for this information that can be verified or this just something you heard in a cantina? -- Daniel A. Morgan University of Washington damorgan@x.washington.edu (replace 'x' with 'u' to respond)