In an organization that has two applications each with its own Oracle database instance, what are the disadvantages of consolidating the two databases into one database with two schemas?
Backups and replicating the database are bigger and slower, probably. What else?
Some background:
The two databases are the “gold source” for their respective data. Each is critical to the operation of the organization and each is actually used by several appliations, tools, and reports (but each database is principally “owned” by one application). The need to join data across the databases, to relate entities in one to entities in the other, comes up frequently. For this reason there are DB links connecting the two and some cross-database materialized views to help with performance. There is an effort underway to reduce data duplication and these materialized views are under discussion. Some in the organization want to phase out DB links and materialized views and introduce more web services to make the data available across applications. My concern is that there are too many situations that require complex joins of data across the two databases so services that expose the data won’t perform. Another approach for reducing DB links and materialized views is to consolidate the schemas into one database, but I want to make sure I’m not forgetting any critical disadvantages to that approach.
In a single consolidated database, you will lose some flexibility from a DBA point of view:
Overall, you will have less administration tasks (a single backup, single patching…) but each task will be more critical since they will have a global effect.
On the development side, beware of namespace collisions: some features are global over a single database, for example:
This means that you will have some work to do if you want to consolidate two databases that have public synonyms with the same name that points to two different things.