Re: DBEXPORT question

Kerry <dino@ix.netcom.com> wrote in article <5ojaen$mrg@dfw-ixnews4.ix.netcom.com>... > Greetings! > > We are running a 5 spindle RAID Level 5 with Fast/Narrow SCSI. The > data and parity are spread over the 5 drives. We have been told that > we should create more than one DBSPACE for data AND for TEMP. > > The current problem is that we are DBEXPORT'ing from a single dbspace > database in Version 5.03. Can we divide that out and DBIMPORT to > multiple dbspaces on the Version 7.21 platform? You can edit the ".sql" file produced by the dbexport to include the appropriate "in" clause on each "create table" and/or "create index" statement. When the dbimport runs, the tables and/or indexes will be placed accordingly, BUT ... In the situation you have described (a single RAID 5 array) if you divide that array in to multiple dbspaces you will make it look to Informix as if there is more than one physical drive which may cause Informix to try do do things like parallel scans. Since your data will be sperad across all five drives in EACH dbspace, this may cause serious head contention, thus slowing things down instead of speeding things up! From a performance and tuning flexibility standpoint, you're usually better off with mirroring rather than RAID 5. Of course then you need more disks, another controller, etc. If your entire instance is to be located on a single RAID 5 array, I would suggest using only three dbspaces: rootdbs, datadbs and tempdbs. Leave your logical & physical logs in the root dbspace in this case and put your databas(es) in the datadbs. 'tempdbs' is of course a temporary dbspace. By keeping all of your data tables in a single dbspace, you will stop the engine from trying to do parallel scans. Moving logs to a different dbspace would serve no purpose here, since they'll be on the same array. The temporary dbspace is still a good idea because it is not logged and thus writes to it will not cause writes to the logs which would otherwise cause extra head movement on the array. DISCLAIMER: These are all very general theoretically based guidelines. Depending on your situation, YMMV. -- Irwin Goldstein Objective Software Systems, Inc. http://www.objectsoft.com