> I want to use SAP DB for 4 separate internal applications - > now I have to > make the decision of using 4 DB-instance or using 1 instance with 4 > different users. > I would prefer using 4 instances because in that way I can > make separate > backups - and recoveries if necessary.
The main drawback of having multiple instances is that the main ressources (sessions, memory) can't be shared across instances. So you'll have to configure each instance for the maximum expected load instead of configuring one instance for the maximum combined load of all applications. Distributing I/O over the disks doesn't work as well as in a single instance because the instances will happily write to the same disk at the same time (probably not a real problem when using RAID). SAP DB tries to match the number of running tasks to te number of CPUs. This is not possible with multiple instances because you could - restrict the numbers of CPUs per instance, thus having possibly idle CPUs - let the instances compete for all the CPUs, which is less efficient because of additional context switches, Daniel Dittmar -- Daniel Dittmar SAP DB, SAP Labs Berlin [EMAIL PROTECTED] http://www.sapdb.org/ _______________________________________________ sapdb.general mailing list [EMAIL PROTECTED] http://listserv.sap.com/mailman/listinfo/sapdb.general
