When dedicated server process model should be used instead of shared process model

As it turns out, the ODA is factory configured with active-backup bonds. I've tested this to work well without any switch-side LACP/EtherChannel configuration, and each bonded connection may be split across two switches. In my tests, no simulated failure or network reconfiguration caused more than a a few hundred milliseconds worth of network outage.

This means that one can set up an isolated redundant front network for web applications using any layer two switches that are not inherently redundant.

To avoid client connections taking the long way into the company network and back through the other switch (and thus making production dependent on that equipment), one can have a private VLAN that only lives on the two edge switches and on an EtherChannel trunk between them.

As such, only the application servers and the database appliance will exist on that virtual network segment.

I don't see a way to control which path the connections from the application servers take to the database listeners, so the link between the two switches will have to be redundant, less this link becomes a single point of failure. This rules out using unmanaged switches without support for VLAN and either LACP or STP.

Using Cisco Catalyst 2960-series switches, I believe a combination of EtherChannel and Port Fast would be the better choice for a solid independent connection between the two. I would also use Port Fast on the ports for all the bonded connections to ODA and application servers.

Since the production network is isolated, one would need separate network connections for management, backup and connectivity to the rest of the company network.

Naturally, in order for this front production network to be fully self contained, any dependencies to external resources, such as DNS or authentication services, must also be resolved. Ideally production would be able to continue independently, without regard to any faults, ongoing maintenance or network outages anywhere else in the data center or company network.

You'd use a hash value as an identifier for rows of data whenever that's "practical", i.e. you actually need a simple identifier for all your rows, there are no candidate (natural) key fields that are practical (too wide for example), and an ordinary (sequential for instance) generated identifier doesn't cut it (for instance you need that row identifier to be "global" - if the same row was created in two distinct databases, they should have the same identifier).

(One non-trivial example of such a thing would be Git. Each object stored in a git repository is uniquely identified by a SHA-1 hash, which is pretty handy to refer unambiguously to a given commit.)

If you need to use something like that, indeed you'll need to create it yourself with Oracle (adding that hash as a column to the table and indexing it, or with a function-based index).

You could go even further by creating your very own index type with application domain indexes if a plain hash isn't good enough – full-text indexing is, I believe, implemented this way.

There is something built-in to Oracle that is hash-based and doesn't actually need an index to get fast row retrieval: hash clusters. You can theoretically retrieve the target row with as little as a single-block I/O (which normal index+table lookups can't match, and even IOTs can't match unless the table is really small). Do read the When to Use Hash Clusters docs though, they are quite peculiar, and you need a good key (one or more columns) in the first place to use them.