RE: Informix versus oracle

Actually, Oracle has been able to take on-line backups for a long time. There are a few different methods - In each case you can substitute the word dbspace for tablespace, and datafile for chunk for ease of understanding between Informix and Oracle. First it can be scripted using key statements such as "alter tablespace <tablespace name> begin backup;" This will then allow you to backup each datafile - without going in depth too much. You must be running in "archive log mode" for this to work though or you would get an error saying that the instance must be in archive log mode. This has been available since version 7.3 - possibly earlier - I cannot remember when that started. The other option is to use EBU (emergency backup utility) with version 7.3 and older, or RMAN (recovery Manager) as of 8.0 and higher - this would be closer to the same kind of tasks that onbar or ontape use. Again, as above you need to be in archive log mode or it will complain (note that in a cold backup situation this is not the case as the instance will be down, and therefore backups would be considered consistent, but the instance would be unavailable during the time) One of the other major differences is that the logical logs (in Oracle's case they are called either redo logs/archive logs for simplicity sake - there is a small difference in how they are worked as well) - anyway the logical logs are stored in chunks in Informix - in Oracle they are written out to the OS and then backed up from there (though they can be configured to write to multiple locations such as both tape and disk and remote network server). So, to answer the question without going in depth is that Oracle has been able to do this for some time. Unfortunately, it has been my experience that Informix's backup is much more efficient since it does not need to be in any special mode essentially, and no extensive scripts are needed to issue a simple ontape/onbar command (I have not delved in to onarchive, so I cannot site anything there) Also note that I believe recovery is also easier with Informix - again due to the lack of need for any complex scripts to do a task. Hope this helps explain some differences without going to far in depth into either engine -----Original Message----- From: rkusenet [SMTP:rkusenet@sympatico.ca] Sent: Saturday, June 07, 2003 7:33 AM To: informix-list@iiug.org Subject: Re: Informix versus oracle "Andy Kent" <andykent@cix.co.uk> wrote > Can't remember whether Oracle allows you do do backups with users all > still fully on-line but I think Informix is / was several years ahead > on that one. Is this true??? Oracle can't support on-line backup!!!! Sounds ridiculous to me. The problem is, in this newsgroup, lot of anti oracle claims have to be taken with a handful of the needful. rk-

Dusty Haas wrote: > Actually, Oracle has been able to take on-line backups for a long time. > > There are a few different methods - Thanks for the explanation. > [...] You must be running in "archive log mode" for this to work > though or you would get an error saying that the instance must be in > archive log mode. [...] What is the significance of 'archive log mode'? Does it place restrictions on what can happen to the database(s) while the system is in that mode? What restrictions? -- Jonathan Leffler #include <disclaimer.h> Email: jleffler@earthlink.net, jleffler@us.ibm.com Guardian of DBD::Informix v2003.04 -- http://dbi.perl.org/

Jonathan Leffler wrote: > Dusty Haas wrote: > >> Actually, Oracle has been able to take on-line backups for a long time. >> >> There are a few different methods - > > > > Thanks for the explanation. It's useful, but not quite 100% correct. You need to look at the doc to get a full view - suggest you start with the Backup and Recovery Concepts - http://download-east.oracle.com/docs/cd/B10501_01/server.920/a96519/intro.htm#BROVW001 Note that you may need a logon to OTN, but it's free, and we won't bite (much) >> [...] You must be running in "archive log mode" for this to work >> though or you would get an error saying that the instance must be in >> archive log mode. [...] > > > > What is the significance of 'archive log mode'? Does it place > restrictions on what can happen to the database(s) while the system is > in that mode? What restrictions? > Archive log mode means that the current redo logs are being copied to another destination after they are used (after a log switch), so that they can become available for re-use as required.