Re: Does this happen to you at work?

On 5/10/05, david wendelken <davewendelken_at_earthlink.net> wrote:
> Short of national security concerns, why would you want the extra overhea=
d of two additional database instances instead of just using three schemas = in one instance?

Various reasons. The main ones are around mobility and political infightin= g.

As separate instances if we need to move a database from one server to another (say the server is overloaded so we need to move one of the databases to a new server or one that's not so heavily loaded) then it's just a case of copy the files over (or even just change some NFS mounts) and we can bring it up on a new server. Change some network settings and we're ready to go. Also if for some reason we need to migrate one of the apps to a later version of Oracle but can't migrate the others (maybe the vendors refuse to support the app for a later version of Oracle, it's happened) then we can migrate the database that needs migrating and leave the others as they are.

Political infighting is a bit more complex. Suppose we did have 3 different apps hosted int he same database. If we needed to schedule an outage (say a reorg because we've added more disks) then we can guarantee that no time within the next 12 months will be suitable for all three. If the users of one app say next Thursday is OK then users of one (or both) of the others will say that it can't be then because they absolutely have to run a big batch job then and the whole organisation will collapse around our ears if the database isn't available. Indeed if one user team says that next Thursday is ideal then one (or both) of the others will schedule a big batch job for that day. With separate instances, assuming we don't need to down the whole server and we're not applying a patch, we can shutdown each one as and when we have the OK for an outage.

Stephen
--=20
It's better to ask a silly question than to make a silly assumption.

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