Re: Raw or Buffered device?

"Tsutomu Ogiwara" <tsutomu_ogiwara@hotmail.com> wrote in message news:<bjrkjh$i2q$1@terabinaries.xmission.com>... > Hi Steven. > > It seems problem that you use Blocked device. > > Do you mean as bellow ? > > % ls -l /dev/rdbroot > crw-rw---- .......> > % ls -l /dev/dbroot > brw-rw---- .......> Yes! > If so, anyone can write on /dev/dbroot. > /dev/dbroot is file system. > What you mean 'anyone can write on /dev/dbroo'? I'm sure no file system create on /dev/dbroot. > It is not simple to change the ROOTPATH. > my ROOTSPACE variabe only refer to a symbol link to real /dev/dbroot. can i simply correct the symbol link to /dev/rdbroot w/o disturb my data? > I think the better solution is dbexport -ss your database, initialize your > IDS, then dbimport. > Probably it exists more better solution than I mentioned. > > Regards. > > -- > Tsutomu Ogiwara from Tokyo Japan. > ICQ#:168106592 > > > > > > >From: steven@steven4u.net (steven) > >Reply-To: steven@steven4u.net (steven) > >To: informix-list@iiug.org > >Subject: Raw or Buffered device? > >Date: 11 Sep 2003 19:41:35 -0700 > > > >Hi, group > > > >today i found another problem about my informix. The ROOTPATH pointed > >to /dev/dbroot instead of /dev/rdbroot. in the manul, however, i see > >the chunks should be in a raw device. > > > >is this a problem? can i simplely correct the ROOTPATH to > >/dev/rdbroot with text editor and a reboot? > > > >- > >steven@lczmsoft.com > > _________________________________________________________________ > Add photos to your e-mail with MSN 8. Get 2 months FREE*. > http://join.msn.com/?page=features/featuredemail > > sending to informix-list

> my ROOTSPACE variabe only refer to a symbol link to real /dev/dbroot. > can i simply correct the symbol link to /dev/rdbroot w/o disturb my > data? Why didn't you say so in the first place? :-) Yes, you can do that. Obviously you must shut the database server down whilst you break and re-create the link -- Neil Truby t:01932 724027 Director m:07798 811708 Ardenta Limited e:neil.truby@ardenta.com

steven@steven4u.net (steven) wrote in message news:<1e7ef8d0.0309120258.677d82f3@posting.google.com>... > "Tsutomu Ogiwara" <tsutomu_ogiwara@hotmail.com> wrote in message news:<bjrkjh$i2q$1@terabinaries.xmission.com>... > > Hi Steven. > > > > It seems problem that you use Blocked device. > > > > Do you mean as bellow ? > > > > % ls -l /dev/rdbroot > > crw-rw---- .......> > > > % ls -l /dev/dbroot > > brw-rw---- .......> > > > Yes! > > > If so, anyone can write on /dev/dbroot. > > /dev/dbroot is file system. > > > What you mean 'anyone can write on /dev/dbroo'? I'm sure no file > system create on /dev/dbroot. > > > It is not simple to change the ROOTPATH. > > > > my ROOTSPACE variabe only refer to a symbol link to real /dev/dbroot. > can i simply correct the symbol link to /dev/rdbroot w/o disturb my > data? > > > I think the better solution is dbexport -ss your database, initialize your > > IDS, then dbimport. > > Probably it exists more better solution than I mentioned. > > > > Regards. > > > > -- > > Tsutomu Ogiwara from Tokyo Japan. > > ICQ#:168106592 > > > > > > > > > > > > >From: steven@steven4u.net (steven) > > >Reply-To: steven@steven4u.net (steven) > > >To: informix-list@iiug.org > > >Subject: Raw or Buffered device? > > >Date: 11 Sep 2003 19:41:35 -0700 > > > > > >Hi, group > > > > > >today i found another problem about my informix. The ROOTPATH pointed > > >to /dev/dbroot instead of /dev/rdbroot. in the manul, however, i see > > >the chunks should be in a raw device. > > > > > >is this a problem? can i simplely correct the ROOTPATH to > > >/dev/rdbroot with text editor and a reboot? > > > > > >- > > >steven@lczmsoft.com > > > > _________________________________________________________________ > > Add photos to your e-mail with MSN 8. Get 2 months FREE*. > > http://join.msn.com/?page=features/featuredemail > > > > sending to informix-list I am a bit confused here. You start off by saying your root points to /dev/dbroot but further on in the discussion you claim it points to a symbolic link. I **GUESS** you mean to say that your onconfig points to a symbolic link, but your simbolic link points to /dev/dbroot instead of /dev/rdbroot? In that case it *MIGHT* be a problem if you simply change to link from /dev/dbroot to /dev/rdbroot. WHY? you ask? Well because data is stored differently on /dev/dbroot (which is as Tsutomo Ogiware pointed out a block device) than on /dev/dbroot (which a raw device). What is the difference? Block devices use the OS file IO system and raw devices to not. So, in short. TO BE SURE: perform a full dbexport your instance. THEN (!) shutdown your instance, change the link (and make sure onconfig point to it!) and restart your instance. If it goes wrong you will have to recraate you instance with the proper link in place and perform a dbimport. Make sure you recreate you instance in accordance with your dbexport sql file! Succes Robert A. Reissaus Ibm/Informix consultants RISDI (tm)(r) Amsterdam , the Netherlands r.a.reissaus@risdi.com www.risdi.com

Neil Truby wrote: > > > my ROOTSPACE variabe only refer to a symbol link to real /dev/dbroot. > > can i simply correct the symbol link to /dev/rdbroot w/o disturb my > > data? > > Why didn't you say so in the first place? :-) > Yes, you can do that. Obviously you must shut the database server down > whilst you break and re-create the link Or execute the command very very quickly:-) > > -- > Neil Truby t:01932 724027 > Director m:07798 811708 > Ardenta Limited e:neil.truby@ardenta.com -- Paul Watson # Oninit Ltd # Growing old is mandatory Tel: +44 1436 672201 # Growing up is optional Fax: +44 1436 678693 # Mob: +44 7818 003457 # www.oninit.com #

On Fri, 12 Sep 2003 09:07:37 -0400, Robert A. Reissaus wrote: <SNIP> > I am a bit confused here. You start off by saying your root points to > /dev/dbroot but further on in the discussion you claim it points to a symbolic > link. I **GUESS** you mean to say that your onconfig points to a symbolic > link, but your simbolic link points to /dev/dbroot instead of /dev/rdbroot? > > In that case it *MIGHT* be a problem if you simply change to link from > /dev/dbroot to /dev/rdbroot. WHY? you ask? Well because data is stored > differently on /dev/dbroot (which is as Tsutomo Ogiware pointed out a block > device) than on /dev/dbroot (which a raw device). What is the difference? > Block devices use the OS file IO system and raw devices to not. NO THERE IS NO DIFFERENCE IN THE PHYSICAL STORAGE regardless of whether you read/write /dev/dbroot or /dev/rdbroot. The ONLY difference is that the latter does not go through the OS buffer cache and the former does. The data on disk is identical either way. IT IS PERFECTLY SAFE to just bring the engine down, remove the symbolic link to /dev/dbroot and replace it with an identically named symbolic link to /dev/rdbroot! HOWEVER, there is no harm, and much peace of mind to be gained from taking a level 0 archive before going through this. Any DBA worth his salt would do so and since you are not hurting performance wise there is no harm in taking the time to do so. > So, in short. TO BE SURE: perform a full dbexport your instance. THEN (!) > shutdown your instance, change the link (and make sure onconfig point to it!) > and restart your instance. If it goes wrong you will have to recraate you > instance with the proper link in place and perform a dbimport. Make sure you > recreate you instance in accordance with your dbexport sql file! UNNECCESSARY! Art S. Kagel